diff --git a/chainerx_cc/chainerx/python/routines.cc b/chainerx_cc/chainerx/python/routines.cc
index 8ecc620438bc..d277cdb2b7d6 100644
--- a/chainerx_cc/chainerx/python/routines.cc
+++ b/chainerx_cc/chainerx/python/routines.cc
@@ -979,9 +979,17 @@ void InitChainerxPooling(pybind11::module& m) {
           "pad_mode"_a = "ignore");
 }
 
+void InitChainerxActivation(pybind11::module& m) {
+    m.def("leaky_relu",
+          [](const ArrayBodyPtr& x, Scalar slope) { return MoveArrayBody(LeakyRelu(Array{x}, slope)); },
+          py::arg("x"),
+          py::arg("slope") = 0.2);
+}
+
 }  // namespace
 
 void InitChainerxRoutines(pybind11::module& m) {
+    InitChainerxActivation(m);
     InitChainerxCreation(m);
     InitChainerxIndexing(m);
     InitChainerxLinalg(m);
diff --git a/chainerx_cc/chainerx/routines/activation.cc b/chainerx_cc/chainerx/routines/activation.cc
index 5ec59b3abffe..41b27b48412c 100644
--- a/chainerx_cc/chainerx/routines/activation.cc
+++ b/chainerx_cc/chainerx/routines/activation.cc
@@ -17,6 +17,7 @@
 #include "chainerx/routines/arithmetic.h"
 #include "chainerx/routines/creation.h"
 #include "chainerx/routines/explog.h"
+#include "chainerx/routines/indexing.h"
 #include "chainerx/routines/misc.h"
 #include "chainerx/routines/type_util.h"
 #include "chainerx/scalar.h"
@@ -36,4 +37,11 @@ Array Relu(const Array& x) {
     return Maximum(0, x_cast);
 }
 
+Array LeakyRelu(const Array& x, Scalar slope) {
+    Dtype dtype = internal::GetMathResultDtype(x.dtype());
+    const Array& x_cast = x.dtype() == dtype ? x : x.AsType(dtype);
+    Array zero = ZerosLike(x_cast, x_cast.device());
+    return Where(x_cast >= zero, x_cast, slope * x_cast);
+}
+
 }  // namespace chainerx
diff --git a/chainerx_cc/chainerx/routines/activation.h b/chainerx_cc/chainerx/routines/activation.h
index d1019294fc38..4024b493bc46 100644
--- a/chainerx_cc/chainerx/routines/activation.h
+++ b/chainerx_cc/chainerx/routines/activation.h
@@ -1,9 +1,5 @@
 #pragma once
 
-#include <cstdint>
-
-#include <nonstd/optional.hpp>
-
 #include "chainerx/array.h"
 #include "chainerx/scalar.h"
 
@@ -13,4 +9,6 @@ Array Sigmoid(const Array& x);
 
 Array Relu(const Array& x);
 
+Array LeakyRelu(const Array& x, Scalar slope);
+
 }  // namespace chainerx
diff --git a/tests/chainerx_tests/unit_tests/routines_tests/test_activation.py b/tests/chainerx_tests/unit_tests/routines_tests/test_activation.py
index b47214cd32f4..59062ac1c09c 100644
--- a/tests/chainerx_tests/unit_tests/routines_tests/test_activation.py
+++ b/tests/chainerx_tests/unit_tests/routines_tests/test_activation.py
@@ -72,6 +72,36 @@ def forward_xp(self, inputs, xp):
 ]
 
 
+@op_utils.op_test(['native:0', 'cuda:0'])
+@chainer.testing.parameterize(*(
+    # Special shapes
+    chainer.testing.product({
+        'shape': [(), (0,), (1,), (2, 0, 3), (1, 1, 1), (2, 3)],
+        'in_dtypes,out_dtype': _in_out_dtypes_math_functions,
+        'input': [-2, 2],
+        'contiguous': [None, 'C'],
+    })
+    # Special values
+    + chainer.testing.product({
+        'shape': [(2, 3)],
+        'in_dtypes,out_dtype': _in_out_float_dtypes_math_functions,
+        'input': [0, float('inf'), -float('inf'), float('nan')],
+        'skip_backward_test': [True],
+        'skip_double_backward_test': [True],
+    })
+))
+class TestLeakyRelu(UnaryMathTestBase, op_utils.NumpyOpTest):
+
+    slope = 0.2
+    check_numpy_strides_compliance = False
+
+    def func(self, xp, a):
+        if xp is numpy:
+            expected = numpy.where(a >= 0, a, a * self.slope)
+            return expected
+        return xp.leaky_relu(a, self.slope)
+
+
 @op_utils.op_test(['native:0', 'cuda:0'])
 @chainer.testing.parameterize(*(
     # Special shapes