diff --git a/.github/workflows/examples_test.yml b/.github/workflows/examples_test.yml
index 061d34b8b..b8f5aad3a 100644
--- a/.github/workflows/examples_test.yml
+++ b/.github/workflows/examples_test.yml
@@ -52,6 +52,7 @@ jobs:
         python examples/pretrained_benchmark/logra_wikitext2_gpt2_lds.py --device cpu
         sed -i 's/range(1000)/range(100)/g' examples/customized_retraining/mnist.py
         python examples/customized_retraining/mnist.py --device cpu --path ./tmp/mnist_ckpt
+        python examples/data_cleaning/tracin_dataloader_group.py
     - name: Uninstall the package
       run: |
         pip uninstall -y dattri
diff --git a/dattri/algorithm/tracin.py b/dattri/algorithm/tracin.py
index 9279d6329..6fd816ced 100644
--- a/dattri/algorithm/tracin.py
+++ b/dattri/algorithm/tracin.py
@@ -178,10 +178,12 @@ def attribute(  # noqa: PLR0912
                     grad_t = self.grad_target_func(parameters, test_batch_data)
                     if self.proj_params.proj_dim is not None:
                         # define the projector for this batch of data
+                        # use grad_t.shape[0] (not test_batch_data[0]) to support
+                        # DataloaderGroup where test_batch_data is a DataLoader
                         self.test_random_project = random_project(
                             grad_t,
                             proj_params=RandomProjectionParams(
-                                feature_batch_size=test_batch_data[0].shape[0],
+                                feature_batch_size=grad_t.shape[0],
                                 device=self.device,
                                 **self.proj_params.model_dump(),
                             ),
diff --git a/dattri/task.py b/dattri/task.py
index fc57f3cba..e7d29b49f 100644
--- a/dattri/task.py
+++ b/dattri/task.py
@@ -2,11 +2,11 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Union
 
 if TYPE_CHECKING:
     from collections.abc import Callable
-    from typing import Dict, List, Optional, Tuple, Union
+    from typing import Dict, List, Optional, Tuple
 
 import inspect
 from pathlib import PosixPath
@@ -14,8 +14,14 @@
 import torch
 from torch import nn
 from torch.func import grad, vmap
+from torch.utils.data import DataLoader
 
-from dattri.func.utils import flatten_func, flatten_params, partial_param
+from dattri.func.utils import (
+    _unflatten_params,
+    flatten_func,
+    flatten_params,
+    partial_param,
+)
 
 
 def _default_checkpoint_load_func(
@@ -52,6 +58,7 @@ def __init__(
         ],
         target_func: Optional[Callable] = None,
         checkpoints_load_func: Optional[Callable] = None,
+        group_target_func: bool = False,
     ) -> None:
         """Initialize the AttributionTask.
 
@@ -88,6 +95,11 @@ def f(params, data):
                 in terms of what is calculated,
                 but it should take the parameters and the data as input. Other than
                 that, the forwarding of model should be in `torch.func` style.
+                When group_target_func=True, target_func is also used for group
+                attribution: it should take (params_dict, batches) where batches
+                is a list of batches from the group DataLoader, and return a scalar
+                (e.g. sum of per-batch losses). The gradient of this scalar w.r.t.
+                params is the test-side gradient for the group.
                 A typical example is as follows:
                 ```python
                 def f(params, data):
@@ -108,8 +120,13 @@ def checkpoints_load_func(model, checkpoint):
                     model.eval()
                     return model
                 ```.
+            group_target_func (bool): If True, enable group attribution: when a
+                DataLoader is passed (e.g. via DataloaderGroup), target_func is
+                called with (params_dict, list_of_batches) and should return a
+                scalar. Default is False.
         """
         self.model = model
+        self.group_target_func = group_target_func
         if target_func is None:
             target_func = loss_func
 
@@ -256,6 +273,32 @@ def get_grad_target_func(
                 randomness="different",
             )
             self.grad_target_func_kwargs = grad_target_func_kwargs
+
+        base_grad_target = self.grad_target_func
+
+        if self.group_target_func:
+            model_ref = self.model
+
+            def wrapped(
+                parameters: torch.Tensor,
+                data: Union[DataLoader, object],
+            ) -> torch.Tensor:
+                if isinstance(data, DataLoader):
+                    # Pre-fetch batches outside grad to avoid tracing DataLoader/dataset
+                    # access (e.g. .numpy() in dataset __getitem__) which can raise
+                    # "Tensor that doesn't have storage" when run inside autograd.
+                    batches = list(data)
+
+                    def flat_group_target(flat_params: torch.Tensor) -> torch.Tensor:
+                        params_dict = _unflatten_params(flat_params, model_ref)
+                        return self.original_target_func(params_dict, batches)
+
+                    g = grad(flat_group_target)(parameters)
+                    return g.unsqueeze(0)
+                return base_grad_target(parameters, data)
+
+            return wrapped
+
         return self.grad_target_func
 
     def get_target_func(
diff --git a/examples/data_cleaning/tracin_dataloader_group.py b/examples/data_cleaning/tracin_dataloader_group.py
new file mode 100644
index 000000000..b77a4e4e8
--- /dev/null
+++ b/examples/data_cleaning/tracin_dataloader_group.py
@@ -0,0 +1,136 @@
+"""This example shows how to use TracInAttributor with DataloaderGroup and
+group_target_func=True so target_func is used for group attribution.
+Uses MNIST + MLP.
+"""
+
+import argparse
+from typing import Iterator
+
+import torch
+from torch import nn
+from torch.utils.data import DataLoader
+
+from dattri.algorithm.tracin import TracInAttributor
+from dattri.benchmark.datasets.mnist import create_mnist_dataset, train_mnist_mlp
+from dattri.benchmark.utils import SubsetSampler
+from dattri.task import AttributionTask
+
+
+class DataloaderGroup(DataLoader):
+    """Helper class to wrap a DataLoader for group attribution.
+
+    This wrapper presents the dataloader as a single item (length 1).
+    When iterated, it yields the original dataloader itself, allowing the
+    consumer to treat the entire dataset as one attribution target.
+    """
+
+    def __init__(self, original_test_dataloader: DataLoader) -> None:
+        """Initialize the DataloaderGroup.
+
+        Args:
+            original_test_dataloader (DataLoader):
+                The PyTorch dataloader for individual test data samples
+        """
+        super().__init__(torch.utils.data.TensorDataset(torch.zeros(1)))
+        self.original_test_dataloader = original_test_dataloader
+
+    def __iter__(self) -> Iterator[DataLoader]:
+        """Iterate over the group.
+
+        Yields:
+            DataLoader: Yields the original dataloader as a single object.
+        """
+        yield self.original_test_dataloader
+
+    def __len__(self) -> int:
+        """Return the length of the group wrapper.
+
+        Returns:
+            int: Always 1, as the whole dataset is treated as one group.
+        """
+        return 1
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--device", type=str, default="cuda")
+    parser.add_argument("--seed", type=int, default=0)
+    parser.add_argument("--train_size", type=int, default=10000)
+    parser.add_argument("--test_size", type=int, default=5000)
+    args = parser.parse_args()
+
+    print(args)
+
+    # load the training dataset (same as influence_function_data_cleaning.py)
+    dataset, dataset_test = create_mnist_dataset("./data")
+
+    # for model training, batch size is 64
+    train_loader_full = DataLoader(
+        dataset,
+        batch_size=64,
+        sampler=SubsetSampler(range(args.train_size)),
+    )
+
+    # training samples for attribution; batch size 1000 to speed up
+    train_loader = DataLoader(
+        dataset,
+        batch_size=1000,
+        sampler=SubsetSampler(range(args.train_size)),
+    )
+    test_loader = DataLoader(
+        dataset_test,
+        batch_size=1000,
+        sampler=SubsetSampler(range(args.test_size)),
+    )
+
+    model = train_mnist_mlp(train_loader_full, seed=args.seed)
+    model.to(args.device)
+    model.eval()
+
+    # loss and target in AttributionTask style; match IF example signature.
+    # When group_target_func=True, target_func is also called with (params_dict, list_of_batches).
+    def f(params, data_target_pair):
+        image, label = data_target_pair
+        label = label.view(-1).long()
+        yhat = torch.func.functional_call(model, params, (image,))
+        return nn.CrossEntropyLoss()(yhat, label)
+
+    def target_func(params, data):
+        if isinstance(data, list):
+            # group mode: data is list of (image, label) batches
+            device = next(iter(params.values())).device
+            total = None
+            for image, label in data:
+                image, label = image.to(device), label.to(device)
+                loss = f(params, (image, label))
+                n = image.shape[0]
+                total = loss * n if total is None else total + loss * n
+            return total
+        return f(params, data)
+
+    task = AttributionTask(
+        loss_func=f,
+        model=model,
+        checkpoints=model.state_dict(),
+        target_func=target_func,
+        group_target_func=True,
+    )
+
+    attributor = TracInAttributor(
+        task=task,
+        weight_list=torch.tensor([1.0]),
+        normalized_grad=False,
+        device=args.device,
+    )
+
+    test_group = DataloaderGroup(test_loader)
+    with torch.no_grad():
+        scores = attributor.attribute(train_loader, test_group)
+        scores_temp = attributor.attribute(train_loader, test_loader)
+
+    print("Test Dataloader Group (AttributionTask + group_target_func=True) — MNIST + MLP.")
+    print(f"Score Shape: {scores.shape}")
+    print(f"Calculated Scores (first 10):\n{scores.flatten()[:10]}")
+    print(f"Calculated Scores Temp sum over test (first 10):\n{scores_temp.sum(dim=1)[:10]}")
+    diff = (scores.flatten() - scores_temp.sum(dim=1)).abs()
+    print(f"Max |group - sum(per-test)|: {diff.max().item():.6f}")
diff --git a/test/dattri/algorithm/test_tracin.py b/test/dattri/algorithm/test_tracin.py
index 193b304a8..d572fa8f7 100644
--- a/test/dattri/algorithm/test_tracin.py
+++ b/test/dattri/algorithm/test_tracin.py
@@ -3,6 +3,7 @@
 import copy
 import shutil
 from pathlib import Path
+from typing import Iterator
 
 import torch
 from torch import nn
@@ -574,3 +575,132 @@ def f(params, image_label_pair):
         assert torch.allclose(ckpt_grad_1[1], ckpt_grad_2[1])
 
         shutil.rmtree(path)
+
+    def test_tracin_dataloader(self):
+        """Verify TracIn Group Attribution correctness."""
+
+        class DataloaderGroup(DataLoader):
+            """Helper class to wrap a DataLoader for group attribution.
+
+            This wrapper presents the dataloader as a single item (length 1).
+            When iterated, it yields the original dataloader itself, allowing the
+            consumer to treat the entire dataset as one attribution target.
+            """
+
+            def __init__(self, original_test_dataloader: DataLoader) -> None:
+                """Initialize the DataloaderGroup.
+
+                Args:
+                    original_test_dataloader (DataLoader):
+                        The PyTorch dataloader for individual test data samples
+                """
+                super().__init__(
+                    torch.utils.data.TensorDataset(torch.zeros(1)),
+                )
+                self.original_test_dataloader = original_test_dataloader
+
+            def __iter__(self) -> Iterator[DataLoader]:
+                """Iterate over the group.
+
+                Yields:
+                    DataLoader: Yields the original dataloader as a single object.
+                """
+                yield self.original_test_dataloader
+
+            def __len__(self) -> int:
+                """Return the length of the group wrapper.
+
+                Returns:
+                    int: Always 1, as the whole dataset is treated as one group.
+                """
+                return 1
+
+        train_loader = DataLoader(
+            TensorDataset(
+                torch.randn(20, 1, 28, 28),
+                torch.randint(0, 10, (20,)),
+            ),
+            batch_size=4,
+            shuffle=False,
+        )
+        test_loader = DataLoader(
+            TensorDataset(
+                torch.randn(10, 1, 28, 28),
+                torch.randint(0, 10, (10,)),
+            ),
+            batch_size=2,
+            shuffle=False,
+        )
+
+        model = train_mnist_lr(train_loader)
+
+        # to simlulate multiple checkpoints
+        model_1 = train_mnist_lr(train_loader, epoch_num=1)
+        model_2 = train_mnist_lr(train_loader, epoch_num=2)
+        path = Path("./ckpts")
+        if not path.exists():
+            path.mkdir(parents=True)
+        torch.save(model_1.state_dict(), path / "model_1.pt")
+        torch.save(model_2.state_dict(), path / "model_2.pt")
+
+        checkpoint_list = ["ckpts/model_1.pt", "ckpts/model_2.pt"]
+
+        def f(params, image_label_pair):
+            image, label = image_label_pair
+            image_t = image.unsqueeze(0)
+            label_t = label.unsqueeze(0)
+            loss = nn.CrossEntropyLoss()
+            yhat = torch.func.functional_call(model, params, image_t)
+            return loss(yhat, label_t)
+
+        def target_func(params, data):
+            if isinstance(data, list):
+                loss_fn = nn.CrossEntropyLoss(reduction="sum")
+                total = None
+                for image, label in data:
+                    yhat = torch.func.functional_call(model, params, (image,))
+                    loss = loss_fn(yhat, label.long())
+                    total = loss if total is None else total + loss
+                return total
+            return f(params, data)
+
+        task = AttributionTask(
+            loss_func=f,
+            model=model,
+            checkpoints=checkpoint_list,
+            target_func=target_func,
+            group_target_func=True,
+        )
+
+        attributor = TracInAttributor(
+            task=task,
+            weight_list=torch.ones(len(checkpoint_list)),
+            normalized_grad=False,
+            device="cpu",
+        )
+
+        score_group = attributor.attribute(
+            train_loader,
+            DataloaderGroup(test_loader),
+        )
+
+        assert score_group.shape == (20, 1), (
+            f"Expected shape (20, 1), got {score_group.shape}"
+        )
+
+        score_full = attributor.attribute(
+            train_loader,
+            test_loader,
+        )
+
+        score_full = score_full.sum(
+            dim=1,
+            keepdim=True,
+        )  # Make the shape (N, 1) for comparison
+
+        assert torch.allclose(score_group, score_full, rtol=1e-03, atol=1e-05), (
+            "Score does not match manual calculation."
+        )
+
+        if path.exists():
+            shutil.rmtree(path)