diff --git a/web/cashtab/src/hooks/useWallet.js b/web/cashtab/src/hooks/useWallet.js
--- a/web/cashtab/src/hooks/useWallet.js
+++ b/web/cashtab/src/hooks/useWallet.js
@@ -839,34 +839,8 @@
     };
 
     const validateMnemonic = (mnemonic, wordlist = bip39.wordlists.english) => {
-        let mnemonicTestOutput;
-
-        // temporary validation of wordlist exclusion
-        // to be removed in next diff in stack
-        console.log('english: ' + bip39.wordlists.english);
-        if (
-            !bip39.wordlists.japanese &&
-            !bip39.wordlists.spanish &&
-            !bip39.wordlists.italian &&
-            !bip39.wordlists.french &&
-            !bip39.wordlists.korean &&
-            !bip39.wordlists.czech &&
-            !bip39.wordlists.portuguese &&
-            !bip39.wordlists.chinese_traditional
-        ) {
-            console.log(
-                'bip39 wordlist is excluding japanese, spanish, italian, french, korean, czech, portuguese and chinese',
-            );
-        }
-
         try {
-            mnemonicTestOutput = validateMnemonicWordList(mnemonic, wordlist);
-
-            if (mnemonicTestOutput === 'Valid mnemonic') {
-                return true;
-            } else {
-                return false;
-            }
+            return validateMnemonicWordList(mnemonic, wordlist);
         } catch (err) {
             console.log(err);
             return false;
diff --git a/web/cashtab/src/utils/__tests__/validation.test.js b/web/cashtab/src/utils/__tests__/validation.test.js
--- a/web/cashtab/src/utils/__tests__/validation.test.js
+++ b/web/cashtab/src/utils/__tests__/validation.test.js
@@ -52,23 +52,23 @@
 import * as bip39 from 'bip39';
 
 describe('Validation utils', () => {
-    it(`validateMnemonicWordList() returns a success message for a valid mnemonic`, () => {
+    it(`validateMnemonicWordList() returns true for a valid mnemonic`, () => {
         const validMnemonic =
             'labor tail bulb distance estate collect lecture into smile differ yard legal';
         expect(
             validateMnemonicWordList(validMnemonic, bip39.wordlists.english),
-        ).toBe('Valid mnemonic');
+        ).toBe(true);
     });
-    it(`validateMnemonicWordList() returns an error message for an invalid mnemonic`, () => {
+    it(`validateMnemonicWordList() returns false for an invalid mnemonic`, () => {
         const validMnemonic =
             'labor tail bulb not valid collect lecture into smile differ yard legal';
         expect(
             validateMnemonicWordList(validMnemonic, bip39.wordlists.english),
-        ).toBe('Invalid mnemonic');
+        ).toBe(false);
     });
-    it(`validateMnemonicWordList() returns an error message for an empty mnemonic`, () => {
+    it(`validateMnemonicWordList() returns false for an empty mnemonic`, () => {
         expect(validateMnemonicWordList('', bip39.wordlists.english)).toBe(
-            'Invalid mnemonic',
+            false,
         );
     });
     it(`Returns 'false' if ${currency.ticker} send amount is a valid send amount`, () => {
diff --git a/web/cashtab/src/utils/validation.js b/web/cashtab/src/utils/validation.js
--- a/web/cashtab/src/utils/validation.js
+++ b/web/cashtab/src/utils/validation.js
@@ -2,22 +2,89 @@
 import { currency } from 'components/Common/Ticker.js';
 import { fromSatoshisToXec } from 'utils/cashMethods';
 import cashaddr from 'ecashaddrjs';
-import * as bip39 from 'bip39';
+const createHash = require('create-hash');
 
-// reference: https://github.com/Permissionless-Software-Foundation/bch-js/blob/62e56c832b35731880fe448269818b853c76dd80/src/mnemonic.js#L160-L180
+// bip39 reference: https://github.com/bitcoinjs/bip39/blob/master/src/index.js#L66
 export const validateMnemonicWordList = (mnemonic, wordlist) => {
-    // Preprocess the words
-    const words = mnemonic.split(' ');
-    // Detect blank phrase
-    if (words.length === 0) return 'Blank mnemonic';
+    if (!mnemonic || !wordlist) {
+        return false;
+    }
+    try {
+        // NFKD = Compatibility Decomposition
+        const words = mnemonic.normalize('NFKD').split(' ');
+
+        // Detect blank phrase
+        if (words.length === 0 || words.length % 3 !== 0) {
+            return false;
+        }
 
-    // Check the words are valid
-    const isValid = bip39.validateMnemonic(mnemonic, wordlist);
-    if (!isValid) return 'Invalid mnemonic';
+        // convert word indices to 11 bit binary strings
+        const bits = words
+            .map(word => {
+                const index = wordlist.indexOf(word);
+                if (index === -1) {
+                    return false;
+                }
+                return lpad(index.toString(2), '0', 11);
+            })
+            .join('');
+
+        // split the binary string into ENT/CS
+        const dividerIndex = Math.floor(bits.length / 33) * 32;
+        const entropyBits = bits.slice(0, dividerIndex);
+        const checksumBits = bits.slice(dividerIndex);
+        // calculate the checksum and compare
+        const entropyBytes = entropyBits.match(/(.{1,8})/g).map(binaryToByte);
+        if (
+            entropyBytes.length < 16 ||
+            entropyBytes.length > 32 ||
+            entropyBytes.length % 4 !== 0
+        ) {
+            return false;
+        }
+        const entropy = Buffer.from(entropyBytes);
+        const newChecksum = deriveChecksumBits(entropy);
+        if (newChecksum !== checksumBits) {
+            return false;
+        }
 
-    return 'Valid mnemonic';
+        return true;
+    } catch (err) {
+        console.log('validateMnemonicWordList(): Error validating Mnemonic');
+        throw err;
+    }
 };
 
+/*
+ * helper functions used by validateMnemonicWordList()
+ * binaryToByte()
+ * lpad()
+ * bytesToBinary()
+ * deriveChecksumBits()
+ */
+// https://github.com/bitcoinjs/bip39/blob/d527196f6f5837b6ac3e2bf4829758ad4f1b1d5c/src/index.js#L35
+function binaryToByte(bin) {
+    return parseInt(bin, 2);
+}
+// https://github.com/bitcoinjs/bip39/blob/d527196f6f5837b6ac3e2bf4829758ad4f1b1d5c/src/index.js#L29
+function lpad(str, padString, length) {
+    while (str.length < length) {
+        str = padString + str;
+    }
+    return str;
+}
+// https://github.com/bitcoinjs/bip39/blob/d527196f6f5837b6ac3e2bf4829758ad4f1b1d5c/src/index.js#L38
+function bytesToBinary(bytes) {
+    return bytes.map(x => lpad(x.toString(2), '0', 8)).join('');
+}
+// https://github.com/bitcoinjs/bip39/blob/d527196f6f5837b6ac3e2bf4829758ad4f1b1d5c/src/index.js#L41
+function deriveChecksumBits(entropyBuffer) {
+    const ENT = entropyBuffer.length * 8;
+    const CS = ENT / 32;
+    const hash = createHash('sha256').update(entropyBuffer).digest();
+    return bytesToBinary(Array.from(hash)).slice(0, CS);
+}
+
 // Validate cash amount
 export const shouldRejectAmountInput = (
     cashAmount,