diff --git a/modules/gapi/src/api/s11n.cpp b/modules/gapi/src/api/s11n.cpp
index 989cc79118..b86cd8f278 100644
--- a/modules/gapi/src/api/s11n.cpp
+++ b/modules/gapi/src/api/s11n.cpp
@@ -141,5 +141,4 @@ cv::GRunArg cv::gapi::bind(cv::GRunArgP &out)
         GAPI_Error("This value type is UNKNOWN!");
         break;
     }
-    return cv::GRunArg();
 }
diff --git a/modules/gapi/src/backends/common/serialization.cpp b/modules/gapi/src/backends/common/serialization.cpp
index 6fe924e61b..a9cfd1a564 100644
--- a/modules/gapi/src/backends/common/serialization.cpp
+++ b/modules/gapi/src/backends/common/serialization.cpp
@@ -206,22 +206,20 @@ IOStream& operator<< (IOStream& os, const cv::RMat& mat) {
     mat.serialize(os);
     return os;
 }
-IIStream& operator>> (IIStream& is, cv::RMat&) {
+IIStream& operator>> (IIStream&, cv::RMat&) {
     util::throw_error(std::logic_error("operator>> for RMat should never be called. "
                                         "Instead, cv::gapi::deserialize<cv::GRunArgs, AdapterTypes...>() "
                                         "should be used"));
-    return is;
 }
 
 IOStream& operator<< (IOStream& os, const cv::MediaFrame &frame) {
     frame.serialize(os);
     return os;
 }
-IIStream& operator>> (IIStream& is, cv::MediaFrame &) {
+IIStream& operator>> (IIStream&, cv::MediaFrame &) {
     util::throw_error(std::logic_error("operator>> for MediaFrame should never be called. "
                                         "Instead, cv::gapi::deserialize<cv::GRunArgs, AdapterTypes...>() "
                                         "should be used"));
-    return is;
 }
 
 namespace
@@ -400,22 +398,19 @@ IOStream& operator<< (IOStream& os, const cv::UMat &)
     GAPI_Error("Serialization: Unsupported << for UMat");
     return os;
 }
-IIStream& operator >> (IIStream& is, cv::UMat &)
+IIStream& operator >> (IIStream&, cv::UMat &)
 {
     GAPI_Error("Serialization: Unsupported >> for UMat");
-    return is;
 }
 #endif // !defined(GAPI_STANDALONE)
 
-IOStream& operator<< (IOStream& os, const cv::gapi::wip::IStreamSource::Ptr &)
+IOStream& operator<< (IOStream&, const cv::gapi::wip::IStreamSource::Ptr &)
 {
     GAPI_Error("Serialization: Unsupported << for IStreamSource::Ptr");
-    return os;
 }
-IIStream& operator >> (IIStream& is, cv::gapi::wip::IStreamSource::Ptr &)
+IIStream& operator >> (IIStream&, cv::gapi::wip::IStreamSource::Ptr &)
 {
-    GAPI_Assert("Serialization: Unsupported >> for IStreamSource::Ptr");
-    return is;
+    GAPI_Error("Serialization: Unsupported >> for IStreamSource::Ptr");
 }
 
 namespace
diff --git a/modules/gapi/src/backends/fluid/gfluidbackend.cpp b/modules/gapi/src/backends/fluid/gfluidbackend.cpp
index d24dcd599a..f363c6165c 100644
--- a/modules/gapi/src/backends/fluid/gfluidbackend.cpp
+++ b/modules/gapi/src/backends/fluid/gfluidbackend.cpp
@@ -313,7 +313,7 @@ static int maxLineConsumption(const cv::GFluidKernel::Kind kind, int window, int
         }
     } break;
     case cv::GFluidKernel::Kind::YUV420toRGB: return inPort == 0 ? 2 : 1; break;
-    default: GAPI_Error("InternalError"); return 0;
+    default: GAPI_Error("InternalError");
     }
 }
 
@@ -325,7 +325,7 @@ static int borderSize(const cv::GFluidKernel::Kind kind, int window)
     // Resize never reads from border pixels
     case cv::GFluidKernel::Kind::Resize: return 0; break;
     case cv::GFluidKernel::Kind::YUV420toRGB: return 0; break;
-    default: GAPI_Error("InternalError"); return 0;
+    default: GAPI_Error("InternalError");
     }
 }
 
diff --git a/modules/gapi/src/backends/fluid/gfluidbuffer.cpp b/modules/gapi/src/backends/fluid/gfluidbuffer.cpp
index 2bdbbbecd6..6cbe2dc369 100644
--- a/modules/gapi/src/backends/fluid/gfluidbuffer.cpp
+++ b/modules/gapi/src/backends/fluid/gfluidbuffer.cpp
@@ -90,7 +90,7 @@ void fillBorderConstant(int borderSize, cv::Scalar borderValue, cv::Mat& mat)
         case CV_16S: return &fillConstBorderRow< int16_t>; break;
         case CV_16U: return &fillConstBorderRow<uint16_t>; break;
         case CV_32F: return &fillConstBorderRow< float  >; break;
-        default: GAPI_Error("InternalError"); return &fillConstBorderRow<uint8_t>;
+        default: GAPI_Error("InternalError");
         }
     };
 
diff --git a/modules/gapi/src/executor/gstreamingexecutor.cpp b/modules/gapi/src/executor/gstreamingexecutor.cpp
index 6a397faca6..67ad18dfa2 100644
--- a/modules/gapi/src/executor/gstreamingexecutor.cpp
+++ b/modules/gapi/src/executor/gstreamingexecutor.cpp
@@ -1830,7 +1830,6 @@ bool cv::gimpl::GStreamingExecutor::pull(cv::GRunArgsP &&outs)
         default:
             GAPI_Error("Unsupported cmd type in pull");
     }
-    GAPI_Error("Unreachable code");
 }
 
 bool cv::gimpl::GStreamingExecutor::pull(cv::GOptRunArgsP &&outs)
diff --git a/modules/gapi/test/streaming/gapi_streaming_tests.cpp b/modules/gapi/test/streaming/gapi_streaming_tests.cpp
index 10f8df820f..343790cc88 100644
--- a/modules/gapi/test/streaming/gapi_streaming_tests.cpp
+++ b/modules/gapi/test/streaming/gapi_streaming_tests.cpp
@@ -327,7 +327,6 @@ public:
 
         if (m_curr_frame_id % m_throw_every_nth_frame == 0) {
             throw std::logic_error(InvalidSource::exception_msg());
-            return true;
         } else {
             d = cv::Mat(m_mat);
         }