diff --git a/src/init.cpp b/src/init.cpp
index 149338eb7081b..3a84442c70031 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -316,6 +316,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-alertnotify=<cmd>", _("Execute command when a relevant alert is received or we see a really long fork (%s in cmd is replaced by message)"));
     strUsage += HelpMessageOpt("-alerts", strprintf(_("Receive and display P2P network alerts (default: %u)"), DEFAULT_ALERTS));
     strUsage += HelpMessageOpt("-blocknotify=<cmd>", _("Execute command when the best block changes (%s in cmd is replaced by block hash)"));
+    strUsage += HelpMessageOpt("-blocksizenotify=<cmd>", _("Execute command when the best block changes and its size is over (%s in cmd is replaced by block hash, %d with the block size)"));
     strUsage += HelpMessageOpt("-checkblocks=<n>", strprintf(_("How many blocks to check at startup (default: %u, 0 = all)"), 500));
     strUsage += HelpMessageOpt("-conf=<file>", strprintf(_("Specify configuration file (default: %s)"), "pivx.conf"));
     if (mode == HMM_BITCOIND) {
@@ -552,6 +553,15 @@ static void BlockNotifyCallback(const uint256& hashNewTip)
     boost::thread t(runCommand, strCmd); // thread runs free
 }
 
+static void BlockSizeNotifyCallback(int size, const uint256& hashNewTip)
+{
+    std::string strCmd = GetArg("-blocksizenotify", "");
+
+    boost::replace_all(strCmd, "%s", hashNewTip.GetHex());
+    boost::replace_all(strCmd, "%d", std::to_string(size));
+    boost::thread t(runCommand, strCmd); // thread runs free
+}
+
 struct CImportingNow {
     CImportingNow()
     {
@@ -1580,6 +1590,9 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     if (mapArgs.count("-blocknotify"))
         uiInterface.NotifyBlockTip.connect(BlockNotifyCallback);
 
+    if (mapArgs.count("-blocksizenotify"))
+        uiInterface.NotifyBlockSize.connect(BlockSizeNotifyCallback);
+
     // scan for better chains in the block chain database, that are not yet connected in the active best chain
     CValidationState state;
     if (!ActivateBestChain(state))
diff --git a/src/main.cpp b/src/main.cpp
index 2ab24d04c10f5..1bfc7b99efb45 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4114,6 +4114,12 @@ bool ActivateBestChain(CValidationState& state, CBlock* pblock, bool fAlreadyChe
             }
             // Notify external listeners about the new tip.
             uiInterface.NotifyBlockTip(hashNewTip);
+
+            unsigned size = GetSerializeSize(*pblock, SER_NETWORK, PROTOCOL_VERSION);
+            // If the size is over 1 MB notify external listeners, and it is within the last 5 minutes
+            if (size > MAX_BLOCK_SIZE_LEGACY && pblock->GetBlockTime() > GetAdjustedTime() - 300) {
+                uiInterface.NotifyBlockSize(static_cast<int>(size), hashNewTip);
+            }
         }
     } while (pindexMostWork != chainActive.Tip());
     CheckBlockIndex();
diff --git a/src/ui_interface.h b/src/ui_interface.h
index 744b32e7dbf3d..bee72b2342eb3 100644
--- a/src/ui_interface.h
+++ b/src/ui_interface.h
@@ -102,6 +102,9 @@ class CClientUIInterface
     /** New block has been accepted */
     boost::signals2::signal<void(const uint256& hash)> NotifyBlockTip;
 
+    /** New block has been accepted and is over a certain size */
+    boost::signals2::signal<void(int size, const uint256& hash)> NotifyBlockSize;
+
     /** Banlist did change. */
     boost::signals2::signal<void (void)> BannedListChanged;
 };