diff --git a/qa/rpc-tests/wallet.py b/qa/rpc-tests/wallet.py
index 493f9891..cde7c1aa 100755
--- a/qa/rpc-tests/wallet.py
+++ b/qa/rpc-tests/wallet.py
@@ -244,6 +244,52 @@ class WalletTest (BitcoinTestFramework):
         myvjoinsplits = mytxdetails["vjoinsplit"]
         assert_equal(0, len(myvjoinsplits))
 
+        # z_sendmany is expected to fail if tx size breaks limit
+        myzaddr = self.nodes[0].z_getnewaddress()
+
+        recipients = []
+        num_t_recipients = 3000
+        amount_per_recipient = Decimal('0.00000001')
+        errorString = ''
+        for i in xrange(0,num_t_recipients):
+            newtaddr = self.nodes[2].getnewaddress()
+            recipients.append({"address":newtaddr, "amount":amount_per_recipient})
+        try:
+            self.nodes[0].z_sendmany(myzaddr, recipients)
+        except JSONRPCException,e:
+            errorString = e.error['message']
+        assert("Too many outputs, size of raw transaction" in errorString)
+
+        recipients = []
+        num_t_recipients = 2000
+        num_z_recipients = 50
+        amount_per_recipient = Decimal('0.00000001')
+        errorString = ''
+        for i in xrange(0,num_t_recipients):
+            newtaddr = self.nodes[2].getnewaddress()
+            recipients.append({"address":newtaddr, "amount":amount_per_recipient})
+        for i in xrange(0,num_z_recipients):
+            newzaddr = self.nodes[2].z_getnewaddress()
+            recipients.append({"address":newzaddr, "amount":amount_per_recipient})
+        try:
+            self.nodes[0].z_sendmany(myzaddr, recipients)
+        except JSONRPCException,e:
+            errorString = e.error['message']
+        assert("size of raw transaction would be larger than limit" in errorString)
+
+        recipients = []
+        num_z_recipients = 100
+        amount_per_recipient = Decimal('0.00000001')
+        errorString = ''
+        for i in xrange(0,num_z_recipients):
+            newzaddr = self.nodes[2].z_getnewaddress()
+            recipients.append({"address":newzaddr, "amount":amount_per_recipient})
+        try:
+            self.nodes[0].z_sendmany(myzaddr, recipients)
+        except JSONRPCException,e:
+            errorString = e.error['message']
+        assert("Invalid parameter, too many zaddr outputs" in errorString)
+
         # add zaddr to node 2
         myzaddr = self.nodes[2].z_getnewaddress()
 
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 77d7773f..7356a0c7 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3166,6 +3166,17 @@ Value z_getoperationstatus_IMPL(const Array& params, bool fRemoveFinishedOperati
     return ret;
 }
 
+
+// Here we define the maximum number of zaddr outputs that can be included in a transaction.
+// If input notes are small, we might actually require more than one joinsplit per zaddr output.
+// For now though, we assume we use one joinsplit per zaddr output (and the second output note is change).
+// We reduce the result by 1 to ensure there is room for non-joinsplit CTransaction data.
+#define Z_SENDMANY_MAX_ZADDR_OUTPUTS    ((MAX_TX_SIZE / JSDescription().GetSerializeSize(SER_NETWORK, PROTOCOL_VERSION)) - 1)
+
+// transaction.h comment: spending taddr output requires CTxIn >= 148 bytes and typical taddr txout is 34 bytes
+#define CTXIN_SPEND_DUST_SIZE   148
+#define CTXOUT_REGULAR_SIZE     34
+
 Value z_sendmany(const Array& params, bool fHelp)
 {
     if (!EnsureWalletIsAvailable(fHelp))
@@ -3177,6 +3188,7 @@ Value z_sendmany(const Array& params, bool fHelp)
             "\nSend multiple times. Amounts are double-precision floating point numbers."
             "\nChange from a taddr flows to a new taddr address, while change from zaddr returns to itself."
             "\nWhen sending coinbase UTXOs to a zaddr, change is not alllowed. The entire value of the UTXO(s) must be consumed."
+            + strprintf("\nCurrently, the maximum number of zaddr outputs is %d due to transaction size limits.\n", Z_SENDMANY_MAX_ZADDR_OUTPUTS)
             + HelpRequiringPassphrase() + "\n"
             "\nArguments:\n"
             "1. \"fromaddress\"         (string, required) The taddr or zaddr to send the funds from.\n"
@@ -3284,6 +3296,30 @@ Value z_sendmany(const Array& params, bool fHelp)
         }
     }
 
+    // Check the number of zaddr outputs does not exceed the limit.
+    if (zaddrRecipients.size() > Z_SENDMANY_MAX_ZADDR_OUTPUTS)  {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, too many zaddr outputs");
+    }
+
+    // As a sanity check, estimate and verify that the size of the transaction will be valid.
+    // Depending on the input notes, the actual tx size may turn out to be larger and perhaps invalid.
+    size_t txsize = 0;
+    CMutableTransaction mtx;
+    mtx.nVersion = 2;
+    for (int i = 0; i < zaddrRecipients.size(); i++) {
+        mtx.vjoinsplit.push_back(JSDescription());
+    }
+    CTransaction tx(mtx);
+    txsize += tx.GetSerializeSize(SER_NETWORK, tx.nVersion);
+    if (fromTaddr) {
+        txsize += CTXIN_SPEND_DUST_SIZE;
+        txsize += CTXOUT_REGULAR_SIZE;      // There will probably be taddr change
+    }
+    txsize += CTXOUT_REGULAR_SIZE * taddrRecipients.size();
+    if (txsize > MAX_TX_SIZE) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Too many outputs, size of raw transaction would be larger than limit of %d bytes", MAX_TX_SIZE ));
+    }
+
     // Minimum confirmations
     int nMinDepth = 1;
     if (params.size() > 2) {