diff --git a/internal/frontend/bridge-gui/bridge-gui/CMakeLists.txt b/internal/frontend/bridge-gui/bridge-gui/CMakeLists.txt
index 9d12c5f8..a5f9b03c 100644
--- a/internal/frontend/bridge-gui/bridge-gui/CMakeLists.txt
+++ b/internal/frontend/bridge-gui/bridge-gui/CMakeLists.txt
@@ -105,9 +105,9 @@ if (NOT TARGET bridgepp)
 endif()
 
 if (APPLE)
-    set(DOCK_ICON_SRC_FILE DockIcon/DockIcon.mm)
+    set(DOCK_ICON_SRC_FILE MacOS/DockIcon.mm)
 else()
-    set(DOCK_ICON_SRC_FILE DockIcon/DockIcon.cpp)
+    set(DOCK_ICON_SRC_FILE MacOS/DockIcon.cpp)
 endif()
 
 if(UNIX)
@@ -125,9 +125,15 @@ add_executable(bridge-gui
     QMLBackend.cpp QMLBackend.h
     UserList.cpp UserList.h
     SentryUtils.cpp SentryUtils.h
-    ${DOCK_ICON_SRC_FILE} DockIcon/DockIcon.h
+    ${DOCK_ICON_SRC_FILE} MacOS/DockIcon.h
     )
 
+
+if (APPLE)
+    target_sources(bridge-gui PRIVATE MacOS/SecondInstance.mm MacOS/SecondInstance.h)
+endif(APPLE)
+
+
 if (WIN32) # on Windows, we add a (non-Qt) resource file that contains the application icon and version information.
     string(TIMESTAMP BRIDGE_BUILD_YEAR "%Y")
     set(REGEX_NUMBER "[0123456789]") # CMake matches does not support \d.
diff --git a/internal/frontend/bridge-gui/bridge-gui/DockIcon/DockIcon.cpp b/internal/frontend/bridge-gui/bridge-gui/MacOS/DockIcon.cpp
similarity index 100%
rename from internal/frontend/bridge-gui/bridge-gui/DockIcon/DockIcon.cpp
rename to internal/frontend/bridge-gui/bridge-gui/MacOS/DockIcon.cpp
diff --git a/internal/frontend/bridge-gui/bridge-gui/DockIcon/DockIcon.h b/internal/frontend/bridge-gui/bridge-gui/MacOS/DockIcon.h
similarity index 100%
rename from internal/frontend/bridge-gui/bridge-gui/DockIcon/DockIcon.h
rename to internal/frontend/bridge-gui/bridge-gui/MacOS/DockIcon.h
diff --git a/internal/frontend/bridge-gui/bridge-gui/DockIcon/DockIcon.mm b/internal/frontend/bridge-gui/bridge-gui/MacOS/DockIcon.mm
similarity index 100%
rename from internal/frontend/bridge-gui/bridge-gui/DockIcon/DockIcon.mm
rename to internal/frontend/bridge-gui/bridge-gui/MacOS/DockIcon.mm
diff --git a/internal/frontend/bridge-gui/bridge-gui/MacOS/SecondInstance.h b/internal/frontend/bridge-gui/bridge-gui/MacOS/SecondInstance.h
new file mode 100644
index 00000000..1fc4708a
--- /dev/null
+++ b/internal/frontend/bridge-gui/bridge-gui/MacOS/SecondInstance.h
@@ -0,0 +1,28 @@
+// Copyright (c) 2023 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+
+#ifndef BRIDGE_GUI_APP_DELEGATE_H
+#define BRIDGE_GUI_APP_DELEGATE_H
+#ifdef Q_OS_MACOS
+
+
+void registerSecondInstanceHandler();
+
+
+#endif // Q_OS_MACOS
+#endif //BRIDGE_GUI_APP_DELEGATE_H
diff --git a/internal/frontend/bridge-gui/bridge-gui/MacOS/SecondInstance.mm b/internal/frontend/bridge-gui/bridge-gui/MacOS/SecondInstance.mm
new file mode 100644
index 00000000..2d8449b8
--- /dev/null
+++ b/internal/frontend/bridge-gui/bridge-gui/MacOS/SecondInstance.mm
@@ -0,0 +1,63 @@
+// Copyright (c) 2023 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+
+#include "SecondInstance.h"
+#include "QMLBackend.h"
+#include <bridgepp/Exception/Exception.h>
+#import <Cocoa/Cocoa.h>
+#import <objc/runtime.h>
+
+
+using namespace bridgepp;
+
+
+#ifdef Q_OS_MACOS
+
+
+//****************************************************************************************************************************************************
+/// \brief handle notification of attempt to re-open the application.
+//****************************************************************************************************************************************************
+void applicationShouldHandleReopen(id, SEL) {
+    app().backend().showMainWindow();
+}
+
+
+//****************************************************************************************************************************************************
+/// \brief Register our handler for the NSApplicationDelegate applicationShouldHandleReopen:hasVisibleWindows: method that is called when the user
+/// tries to open a second instance of an application.
+///
+/// Objective-C(++) lets you add or replace selector within a class at runtime. we use it to implement our handler for the
+/// applicationShouldHandleReopen:hasVisibleWindows: selector of the Cocoa application delegate.
+//****************************************************************************************************************************************************
+void registerSecondInstanceHandler() {
+    try {
+        Class cls = [[[NSApplication sharedApplication] delegate] class];
+        if (!cls) {
+            throw Exception("Could not retrieve Cocoa NSApplicationDelegate instance");
+        }
+
+        if (!class_replaceMethod(cls, @selector(applicationShouldHandleReopen:hasVisibleWindows:), (IMP) applicationShouldHandleReopen, "v@:")) {
+            throw Exception("Could not register second application instance handler");
+        }
+    } catch (Exception const &e) {
+        app().log().error(e.qwhat());
+    }
+}
+
+
+#endif //  Q_OS_MACOS
diff --git a/internal/frontend/bridge-gui/bridge-gui/QMLBackend.h b/internal/frontend/bridge-gui/bridge-gui/QMLBackend.h
index 1494f275..0b63f8a4 100644
--- a/internal/frontend/bridge-gui/bridge-gui/QMLBackend.h
+++ b/internal/frontend/bridge-gui/bridge-gui/QMLBackend.h
@@ -20,7 +20,7 @@
 #define BRIDGE_GUI_QML_BACKEND_H
 
 
-#include "DockIcon/DockIcon.h"
+#include "MacOS/DockIcon.h"
 #include "Version.h"
 #include "UserList.h"
 #include <bridgepp/GRPC/GRPCClient.h>
diff --git a/internal/frontend/bridge-gui/bridge-gui/main.cpp b/internal/frontend/bridge-gui/bridge-gui/main.cpp
index 42b38a7a..8db99349 100644
--- a/internal/frontend/bridge-gui/bridge-gui/main.cpp
+++ b/internal/frontend/bridge-gui/bridge-gui/main.cpp
@@ -30,9 +30,16 @@
 #include <project_sentry_config.h>
 
 
-using namespace bridgepp;
+#ifdef Q_OS_MACOS
 
 
+#include "MacOS/SecondInstance.h"
+
+
+#endif
+
+using namespace bridgepp;
+
 namespace {
 
 /// \brief The file extension for the bridge executable file.
@@ -320,6 +327,7 @@ int main(int argc, char *argv[]) {
         CommandLineOptions const cliOptions = parseCommandLine(argc, argv);
 
 #ifdef Q_OS_MACOS
+        registerSecondInstanceHandler();
         setDockIconVisibleState(!cliOptions.noWindow);
 #endif