diff --git a/doc/releases/changelog-dev.md b/doc/releases/changelog-dev.md
index 0adbb3bca7a..2713c21fc81 100644
--- a/doc/releases/changelog-dev.md
+++ b/doc/releases/changelog-dev.md
@@ -238,6 +238,9 @@
   [(#5256)](https://github.com/PennyLaneAI/pennylane/pull/5256)
   [(#5395)](https://github.com/PennyLaneAI/pennylane/pull/5395)
 
+* Add type hints for unimplemented methods of the abstract class `Operator`.
+  [(#5490)](https://github.com/PennyLaneAI/pennylane/pull/5490)
+
 * A clear error message is added in `KerasLayer` when using the newest version of TensorFlow with Keras 3 
   (which is not currently compatible with `KerasLayer`), linking to instructions to enable Keras 2.
   [(#5488)](https://github.com/PennyLaneAI/pennylane/pull/5488)
@@ -411,6 +414,7 @@ Korbinian Kottmann,
 Christina Lee,
 Vincent Michaud-Rioux,
 Mudit Pandey,
+Kenya Sakka,
 Jay Soni,
 Matthew Silverman,
 David Wierichs.
diff --git a/pennylane/operation.py b/pennylane/operation.py
index 7ed697f8635..4a3fe4c726b 100644
--- a/pennylane/operation.py
+++ b/pennylane/operation.py
@@ -248,12 +248,12 @@
 import itertools
 import warnings
 from enum import IntEnum
-from typing import List
+from typing import List, Tuple
 from contextlib import contextmanager
 
 import numpy as np
 from numpy.linalg import multi_dot
-from scipy.sparse import coo_matrix, eye, kron
+from scipy.sparse import coo_matrix, csr_matrix, eye, kron
 
 import pennylane as qml
 from pennylane.math import expand_matrix
@@ -748,7 +748,7 @@ def __hash__(self):
         return self.hash
 
     @staticmethod
-    def compute_matrix(*params, **hyperparams):  # pylint:disable=unused-argument
+    def compute_matrix(*params, **hyperparams) -> TensorLike:  # pylint:disable=unused-argument
         r"""Representation of the operator as a canonical matrix in the computational basis (static method).
 
         The canonical matrix is the textbook matrix representation that does not consider wires.
@@ -774,7 +774,7 @@ def has_matrix(cls):
         """
         return cls.compute_matrix != Operator.compute_matrix or cls.matrix != Operator.matrix
 
-    def matrix(self, wire_order=None):
+    def matrix(self, wire_order=None) -> TensorLike:
         r"""Representation of the operator as a matrix in the computational basis.
 
         If ``wire_order`` is provided, the numerical representation considers the position of the
@@ -809,7 +809,9 @@ def matrix(self, wire_order=None):
         return expand_matrix(canonical_matrix, wires=self.wires, wire_order=wire_order)
 
     @staticmethod
-    def compute_sparse_matrix(*params, **hyperparams):  # pylint:disable=unused-argument
+    def compute_sparse_matrix(
+        *params, **hyperparams
+    ) -> csr_matrix:  # pylint:disable=unused-argument
         r"""Representation of the operator as a sparse matrix in the computational basis (static method).
 
         The canonical matrix is the textbook matrix representation that does not consider wires.
@@ -827,7 +829,7 @@ def compute_sparse_matrix(*params, **hyperparams):  # pylint:disable=unused-argu
         """
         raise SparseMatrixUndefinedError
 
-    def sparse_matrix(self, wire_order=None):
+    def sparse_matrix(self, wire_order=None) -> csr_matrix:
         r"""Representation of the operator as a sparse matrix in the computational basis.
 
         If ``wire_order`` is provided, the numerical representation considers the position of the
@@ -852,7 +854,7 @@ def sparse_matrix(self, wire_order=None):
         return expand_matrix(canonical_sparse_matrix, wires=self.wires, wire_order=wire_order)
 
     @staticmethod
-    def compute_eigvals(*params, **hyperparams):
+    def compute_eigvals(*params, **hyperparams) -> TensorLike:
         r"""Eigenvalues of the operator in the computational basis (static method).
 
         If :attr:`diagonalizing_gates` are specified and implement a unitary :math:`U^{\dagger}`,
@@ -1268,7 +1270,7 @@ def has_decomposition(cls):
             or cls.decomposition != Operator.decomposition
         )
 
-    def decomposition(self):
+    def decomposition(self) -> List["Operator"]:
         r"""Representation of the operator as a product of other operators.
 
         .. math:: O = O_1 O_2 \dots O_n
@@ -1285,7 +1287,7 @@ def decomposition(self):
         )
 
     @staticmethod
-    def compute_decomposition(*params, wires=None, **hyperparameters):
+    def compute_decomposition(*params, wires=None, **hyperparameters) -> List["Operator"]:
         r"""Representation of the operator as a product of other operators (static method).
 
         .. math:: O = O_1 O_2 \dots O_n.
@@ -1324,7 +1326,7 @@ def has_diagonalizing_gates(cls):
     @staticmethod
     def compute_diagonalizing_gates(
         *params, wires, **hyperparams
-    ):  # pylint: disable=unused-argument
+    ) -> List["Operator"]:  # pylint: disable=unused-argument
         r"""Sequence of gates that diagonalize the operator in the computational basis (static method).
 
         Given the eigendecomposition :math:`O = U \Sigma U^{\dagger}` where
@@ -1719,7 +1721,7 @@ def control_wires(self):  # pragma: no cover
         """
         return Wires([])
 
-    def single_qubit_rot_angles(self):
+    def single_qubit_rot_angles(self) -> Tuple[float, float, float]:
         r"""The parameters required to implement a single-qubit gate as an
         equivalent ``Rot`` gate, up to a global phase.
 
@@ -1814,7 +1816,9 @@ class Channel(Operation, abc.ABC):
 
     @staticmethod
     @abc.abstractmethod
-    def compute_kraus_matrices(*params, **hyperparams):  # pylint:disable=unused-argument
+    def compute_kraus_matrices(
+        *params, **hyperparams
+    ) -> List[np.ndarray]:  # pylint:disable=unused-argument
         """Kraus matrices representing a quantum channel, specified in
         the computational basis.