diff --git a/modules/calib3d/src/calibration.cpp b/modules/calib3d/src/calibration.cpp
index c03e3a1c345f..97ddcf357b85 100644
--- a/modules/calib3d/src/calibration.cpp
+++ b/modules/calib3d/src/calibration.cpp
@@ -2808,9 +2808,6 @@ void cvGetOptimalNewCameraMatrix( const CvMat* cameraMatrix, const CvMat* distCo
                                       (double)((inner.y - cy0)*s + cy),
                                       (double)(inner.width*s),
                                       (double)(inner.height*s));
-            cv::Rect r(cvCeil(inner.x), cvCeil(inner.y), cvFloor(inner.width), cvFloor(inner.height));
-            r &= cv::Rect(0, 0, newImgSize.width, newImgSize.height);
-            *validPixROI = cvRect(r);
         }
     }
     else
@@ -2840,11 +2837,39 @@ void cvGetOptimalNewCameraMatrix( const CvMat* cameraMatrix, const CvMat* distCo
         if( validPixROI )
         {
             icvGetRectangles( cameraMatrix, distCoeffs, 0, &matM, imgSize, inner, outer );
-            cv::Rect r = inner;
-            r &= cv::Rect(0, 0, newImgSize.width, newImgSize.height);
-            *validPixROI = cvRect(r);
         }
     }
+    if( validPixROI )
+    {
+        // This tolerance defines how incomplete a pixel can be to still be considered complete.
+        // It has been chosen to get Calib3d_GetOptimalNewCameraMatrixNoDistortion.accuracy to pass.
+        constexpr double kTolerance = 1e-12;
+        Point p1, p2;
+        if( std::abs(inner.x-cvRound(inner.x))<kTolerance ) {
+            p1.x = cvRound(inner.x);
+        } else {
+            p1.x = cvCeil(inner.x);
+        }
+        if( std::abs(inner.y-cvRound(inner.y))<kTolerance ) {
+            p1.y = cvRound(inner.y);
+        } else {
+            p1.y = cvCeil(inner.y);
+        }
+        if( std::abs(inner.x+inner.width-cvRound(inner.x+inner.width))<kTolerance ) {
+            p2.x = cvRound(inner.x+inner.width);
+        } else {
+            p2.x = cvFloor(inner.x+inner.width);
+        }
+        if( std::abs(inner.y+inner.height-cvRound(inner.y+inner.height))<kTolerance ) {
+            p2.y = cvRound(inner.y+inner.height);
+        } else {
+            p2.y = cvCeil(inner.y+inner.height);
+        }
+        // +1 to make sure p2 is included.
+        cv::Rect r(p1, p2+cv::Point(1,1));
+        r &= cv::Rect(0, 0, newImgSize.width, newImgSize.height);
+        *validPixROI = cvRect(r);
+    }
 
     cvConvert(&matM, newCameraMatrix);
 }
diff --git a/modules/calib3d/test/test_undistort.cpp b/modules/calib3d/test/test_undistort.cpp
index 38537c86215b..772bca100dca 100644
--- a/modules/calib3d/test/test_undistort.cpp
+++ b/modules/calib3d/test/test_undistort.cpp
@@ -171,6 +171,7 @@ class CV_GetOptimalNewCameraMatrixNoDistortionTest : public cvtest::ArrayTest
     cv::Mat camera_mat;
     cv::Mat distortion_coeffs;
     cv::Mat new_camera_mat;
+    cv::Rect validPixROI;
 
     cv::Size img_size;
     double alpha;
@@ -187,6 +188,8 @@ CV_GetOptimalNewCameraMatrixNoDistortionTest::CV_GetOptimalNewCameraMatrixNoDist
     test_array[INPUT].push_back(NULL); // camera_mat
     test_array[INPUT].push_back(NULL); // distortion_coeffs
     test_array[OUTPUT].push_back(NULL); // new_camera_mat
+    test_array[OUTPUT].push_back(NULL); // validPixROI
+    test_array[REF_OUTPUT].push_back(NULL);
     test_array[REF_OUTPUT].push_back(NULL);
 
     alpha = 0.0;
@@ -199,7 +202,9 @@ void CV_GetOptimalNewCameraMatrixNoDistortionTest::get_test_array_types_and_size
     cvtest::ArrayTest::get_test_array_types_and_sizes(test_case_idx, sizes, types);
     RNG& rng = ts->get_rng();
     matrix_type = types[INPUT][0] = types[INPUT][1] = types[OUTPUT][0] = types[REF_OUTPUT][0] = cvtest::randInt(rng)%2 ? CV_64F : CV_32F;
+    types[OUTPUT][1] = types[REF_OUTPUT][1] = CV_32S;
     sizes[INPUT][0] = sizes[OUTPUT][0] = sizes[REF_OUTPUT][0] = cvSize(3,3);
+    sizes[OUTPUT][1] = sizes[REF_OUTPUT][1] = Size(4,1);
     sizes[INPUT][1] = cvSize(1,4);
 }
 
@@ -240,7 +245,7 @@ int CV_GetOptimalNewCameraMatrixNoDistortionTest::prepare_test_case(int test_cas
 
 void CV_GetOptimalNewCameraMatrixNoDistortionTest::run_func()
 {
-    new_camera_mat = cv::getOptimalNewCameraMatrix(camera_mat, distortion_coeffs, img_size, alpha, img_size, NULL, center_principal_point);
+    new_camera_mat = cv::getOptimalNewCameraMatrix(camera_mat, distortion_coeffs, img_size, alpha, img_size, &validPixROI, center_principal_point);
 }
 
 void CV_GetOptimalNewCameraMatrixNoDistortionTest::prepare_to_validation(int /*test_case_idx*/)
@@ -248,9 +253,13 @@ void CV_GetOptimalNewCameraMatrixNoDistortionTest::prepare_to_validation(int /*t
     const Mat& src = test_mat[INPUT][0];
     Mat& dst = test_mat[REF_OUTPUT][0];
     cvtest::copy(src, dst);
+    Mat& ref_validPixROI = test_mat[REF_OUTPUT][1];
+    cvtest::copy(cv::Mat(cv::Vec4i(0, 0, img_size.width, img_size.height)), ref_validPixROI);
 
     Mat& output = test_mat[OUTPUT][0];
     cvtest::convert(new_camera_mat, output, output.type());
+    Mat& output_validPixROI = test_mat[OUTPUT][1];
+    cvtest::copy(cv::Mat(cv::Vec4i(validPixROI.x, validPixROI.y, validPixROI.width, validPixROI.height)), output_validPixROI);
 }
 
 //---------

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