diff --git a/Examples/UIExplorer/UIExplorerUnitTests/RCTModuleMethodTests.m b/Examples/UIExplorer/UIExplorerUnitTests/RCTModuleMethodTests.m
index a51319bb3..93ac3b5aa 100644
--- a/Examples/UIExplorer/UIExplorerUnitTests/RCTModuleMethodTests.m
+++ b/Examples/UIExplorer/UIExplorerUnitTests/RCTModuleMethodTests.m
@@ -23,6 +23,7 @@ static BOOL RCTLogsError(void (^block)(void))
 {
   __block BOOL loggedError = NO;
   RCTPerformBlockWithLogFunction(block, ^(RCTLogLevel level,
+                                          __unused RCTLogSource source,
                                           __unused NSString *fileName,
                                           __unused NSNumber *lineNumber,
                                           __unused NSString *message) {
diff --git a/Libraries/RCTTest/RCTTestRunner.m b/Libraries/RCTTest/RCTTestRunner.m
index 13d38247b..1e5cd448e 100644
--- a/Libraries/RCTTest/RCTTestRunner.m
+++ b/Libraries/RCTTest/RCTTestRunner.m
@@ -86,7 +86,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
   @autoreleasepool {
     __block NSString *error = nil;
-    RCTSetLogFunction(^(RCTLogLevel level, NSString *fileName, NSNumber *lineNumber, NSString *message) {
+    RCTSetLogFunction(^(RCTLogLevel level, RCTLogSource source, NSString *fileName, NSNumber *lineNumber, NSString *message) {
       if (level >= RCTLogLevelError) {
         error = message;
       }
diff --git a/React/Base/RCTAssert.m b/React/Base/RCTAssert.m
index 5ba9da708..8923f40a5 100644
--- a/React/Base/RCTAssert.m
+++ b/React/Base/RCTAssert.m
@@ -119,7 +119,7 @@ void _RCTAssertFormat(
 
 void RCTFatal(NSError *error)
 {
-  _RCTLogInternal(RCTLogLevelFatal, NULL, 0, @"%@", [error localizedDescription]);
+  _RCTLogNativeInternal(RCTLogLevelFatal, NULL, 0, @"%@", [error localizedDescription]);
 
   RCTFatalHandler fatalHandler = RCTGetFatalHandler();
   if (fatalHandler) {
diff --git a/React/Base/RCTLog.h b/React/Base/RCTLog.h
index 28a615af8..27cdf3158 100644
--- a/React/Base/RCTLog.h
+++ b/React/Base/RCTLog.h
@@ -45,6 +45,14 @@ typedef NS_ENUM(NSInteger, RCTLogLevel) {
   RCTLogLevelFatal = 4
 };
 
+/**
+ * An enum representing the source of a log message.
+ */
+typedef NS_ENUM(NSInteger, RCTLogSource) {
+  RCTLogSourceNative = 1,
+  RCTLogSourceJavaScript = 2
+};
+
 /**
  * A block signature to be used for custom logging functions. In most cases you
  * will want to pass these arguments to the RCTFormatLog function in order to
@@ -52,6 +60,7 @@ typedef NS_ENUM(NSInteger, RCTLogLevel) {
  */
 typedef void (^RCTLogFunction)(
   RCTLogLevel level,
+  RCTLogSource source,
   NSString *fileName,
   NSNumber *lineNumber,
   NSString *message
@@ -115,9 +124,10 @@ RCT_EXTERN void RCTPerformBlockWithLogPrefix(void (^block)(void), NSString *pref
  * Private logging function - ignore this.
  */
 #if RCTLOG_ENABLED
-#define _RCTLog(lvl, ...) _RCTLogInternal(lvl, __FILE__, __LINE__, __VA_ARGS__);
+#define _RCTLog(lvl, ...) _RCTLogNativeInternal(lvl, __FILE__, __LINE__, __VA_ARGS__);
 #else
 #define _RCTLog(lvl, ...) do { } while (0)
 #endif
 
-RCT_EXTERN void _RCTLogInternal(RCTLogLevel, const char *, int, NSString *, ...) NS_FORMAT_FUNCTION(4,5);
+RCT_EXTERN void _RCTLogNativeInternal(RCTLogLevel, const char *, int, NSString *, ...) NS_FORMAT_FUNCTION(4,5);
+RCT_EXTERN void _RCTLogJavaScriptInternal(RCTLogLevel, NSString *);
diff --git a/React/Base/RCTLog.m b/React/Base/RCTLog.m
index b9360f449..02bc9b660 100644
--- a/React/Base/RCTLog.m
+++ b/React/Base/RCTLog.m
@@ -53,14 +53,13 @@ void RCTSetLogThreshold(RCTLogLevel threshold) {
 
 RCTLogFunction RCTDefaultLogFunction = ^(
   RCTLogLevel level,
+  RCTLogSource source,
   NSString *fileName,
   NSNumber *lineNumber,
   NSString *message
 )
 {
-  NSString *log = RCTFormatLog(
-    [NSDate date], level, fileName, lineNumber, message
-  );
+  NSString *log = RCTFormatLog([NSDate date], level, fileName, lineNumber, message);
   fprintf(stderr, "%s\n", log.UTF8String);
   fflush(stderr);
 
@@ -102,13 +101,9 @@ void RCTAddLogFunction(RCTLogFunction logFunction)
 {
   RCTLogFunction existing = RCTGetLogFunction();
   if (existing) {
-    RCTSetLogFunction(^(RCTLogLevel level,
-                        NSString *fileName,
-                        NSNumber *lineNumber,
-                        NSString *message) {
-
-      existing(level, fileName, lineNumber, message);
-      logFunction(level, fileName, lineNumber, message);
+    RCTSetLogFunction(^(RCTLogLevel level, RCTLogSource source, NSString *fileName, NSNumber *lineNumber, NSString *message) {
+      existing(level, source, fileName, lineNumber, message);
+      logFunction(level, source, fileName, lineNumber, message);
     });
   } else {
     RCTSetLogFunction(logFunction);
@@ -147,8 +142,10 @@ void RCTPerformBlockWithLogPrefix(void (^block)(void), NSString *prefix)
 {
   RCTLogFunction logFunction = RCTGetLocalLogFunction();
   if (logFunction) {
-    RCTPerformBlockWithLogFunction(block, ^(RCTLogLevel level, NSString *fileName, NSNumber *lineNumber, NSString *message) {
-      logFunction(level, fileName, lineNumber, [prefix stringByAppendingString:message]);
+    RCTPerformBlockWithLogFunction(block, ^(RCTLogLevel level, RCTLogSource source,
+                                            NSString *fileName, NSNumber *lineNumber,
+                                            NSString *message) {
+      logFunction(level, source, fileName, lineNumber, [prefix stringByAppendingString:message]);
     });
   }
 }
@@ -192,17 +189,11 @@ NSString *RCTFormatLog(
   return log;
 }
 
-void _RCTLogInternal(
-  RCTLogLevel level,
-  const char *fileName,
-  int lineNumber,
-  NSString *format, ...
-)
+void _RCTLogNativeInternal(RCTLogLevel level, const char *fileName, int lineNumber, NSString *format, ...)
 {
   RCTLogFunction logFunction = RCTGetLocalLogFunction();
   BOOL log = RCT_DEBUG || (logFunction != nil);
   if (log && level >= RCTGetLogThreshold()) {
-
     // Get message
     va_list args;
     va_start(args, format);
@@ -211,7 +202,7 @@ void _RCTLogInternal(
 
     // Call log function
     if (logFunction) {
-      logFunction(level, fileName ? @(fileName) : nil, (lineNumber >= 0) ? @(lineNumber) : nil, message);
+      logFunction(level, RCTLogSourceNative, fileName ? @(fileName) : nil, lineNumber > 0 ? @(lineNumber) : nil, message);
     }
 
 #if RCT_DEBUG
@@ -245,3 +236,14 @@ void _RCTLogInternal(
 #endif
   }
 }
+
+void _RCTLogJavaScriptInternal(RCTLogLevel level, NSString *message)
+{
+  RCTLogFunction logFunction = RCTGetLocalLogFunction();
+  BOOL log = RCT_DEBUG || (logFunction != nil);
+  if (log && level >= RCTGetLogThreshold()) {
+    if (logFunction) {
+      logFunction(level, RCTLogSourceJavaScript, nil, nil, message);
+    }
+  }
+}
diff --git a/React/Executors/RCTContextExecutor.m b/React/Executors/RCTContextExecutor.m
index 59c702025..ee7678298 100644
--- a/React/Executors/RCTContextExecutor.m
+++ b/React/Executors/RCTContextExecutor.m
@@ -126,7 +126,7 @@ static JSValueRef RCTNativeLoggingHook(JSContextRef context, __unused JSObjectRe
       level = MAX(level, JSValueToNumber(context, arguments[1], exception));
     }
 
-    _RCTLog(level, @"%@", message);
+    _RCTLogJavaScriptInternal(level, message);
   }
 
   return JSValueMakeUndefined(context);