diff --git a/modules/core/src/mean.dispatch.cpp b/modules/core/src/mean.dispatch.cpp
index 52c0954ff8..619fae6f89 100644
--- a/modules/core/src/mean.dispatch.cpp
+++ b/modules/core/src/mean.dispatch.cpp
@@ -592,7 +592,8 @@ void meanStdDev(InputArray _src, OutputArray _mean, OutputArray _sdv, InputArray
     uchar* ptrs[2] = {};
     NAryMatIterator it(arrays, ptrs);
     int total = (int)it.size, blockSize = total, intSumBlockSize = 0;
-    int j, count = 0, nz0 = 0;
+    int j;
+    int64_t count = 0, nz0 = 0;
     AutoBuffer<double> _buf(cn*4);
     double *s = (double*)_buf.data(), *sq = s + cn;
     int *sbuf = (int*)s, *sqbuf = (int*)sq;
diff --git a/modules/core/test/test_arithm.cpp b/modules/core/test/test_arithm.cpp
index 332e7d17c6..137f30a13c 100644
--- a/modules/core/test/test_arithm.cpp
+++ b/modules/core/test/test_arithm.cpp
@@ -2814,6 +2814,19 @@ TEST(Core_MeanStdDev, regression_multichannel)
     }
 }
 
+// Related issue : https://github.com/opencv/opencv/issues/26861
+TEST(Core_MeanStdDevTest, LargeImage)
+{
+    applyTestTag(CV_TEST_TAG_VERYLONG);
+    applyTestTag(CV_TEST_TAG_MEMORY_14GB);
+    // (1<<16) * ((1<<15)+10) = ~2.147 billion
+    cv::Mat largeImage = cv::Mat::ones((1 << 16), ((1 << 15) + 10), CV_8U);
+    cv::Scalar mean, stddev;
+    cv::meanStdDev(largeImage, mean, stddev);
+    EXPECT_NEAR(mean[0], 1.0, 1e-5);
+    EXPECT_NEAR(stddev[0], 0.0, 1e-5);
+}
+
 template <typename T> static inline
 void testDivideInitData(Mat& src1, Mat& src2)
 {