diff --git a/package.json b/package.json
index 197e500f..87df5e9a 100644
--- a/package.json
+++ b/package.json
@@ -24,7 +24,7 @@
         "test": "npm run lint:js && npm run validate:editor && npm run validate:www && npm run build && npm run lint:json",
         "update": "scripts/update-translations.sh",
         "validate:blocks": "babel-node scripts/validate-translations ./editor/blocks/",
-        "validate:extensions": "babel-node scripts/validate-translations ./editor/extensions/",
+        "validate:extensions": "babel-node scripts/validate-translations ./editor/extensions/ && babel-node scripts/validate-extension-inputs",
         "validate:interface": "babel-node scripts/validate-translations ./editor/interface/",
         "validate:paint": "babel-node scripts/validate-translations ./editor/paint-editor/",
         "validate:editor": "npm run validate:blocks && npm run validate:extensions && npm run validate:interface && npm run validate:paint",
diff --git a/scripts/validate-extension-inputs.js b/scripts/validate-extension-inputs.js
new file mode 100644
index 00000000..9a374e87
--- /dev/null
+++ b/scripts/validate-extension-inputs.js
@@ -0,0 +1,86 @@
+#!/usr/bin/env babel-node
+
+/**
+ * @fileoverview
+ * Script to validate extension block input placeholders
+ */
+
+import fs from 'fs';
+import path from 'path';
+import async from 'async';
+import assert from 'assert';
+import locales from '../src/supported-locales.js';
+
+// Globals
+const JSON_DIR = path.join(process.cwd(), '/editor/extensions');
+const source = JSON.parse(fs.readFileSync(`${JSON_DIR}/en.json`));
+
+// Matches everything inside brackets, and the brackets themselves.
+// e.g. matches '[MOTOR_ID]', '[POWER]' from 'altera a potência de [MOTOR_ID] para [POWER]'
+const blockInputRegex = /\[.+?\]/g;
+
+let numTotalErrors = 0;
+
+const validateExtensionInputs = (translationData, locale) => {
+    let numLocaleErrors = 0;
+    for (const block of Object.keys(translationData)) {
+        const englishBlockInputs = source[block].match(blockInputRegex);
+
+        if (!englishBlockInputs) continue;
+
+        // If null (meaning no matches), that means that English block inputs exist but translated ones don't.
+        // Coerce it to an empty array so that the assertion below fails, instead of getting the less-helpful error
+        // that we can't call Array.includes on null.
+        const translatedBlockInputs = translationData[block].match(blockInputRegex) || [];
+
+        for (const input of englishBlockInputs) {
+            // Currently there are enough errors here that it would be tedious to fix an error, rerun this tool
+            // to find the next error, and repeat. So, catch the assertion error and add to the number of total errors.
+            // This allows all errors to be displayed when the command is run, rather than just the first encountered.
+            try {
+                assert(
+                    translatedBlockInputs.includes(input),
+
+                    `Block '${block}' in locale '${locale}' does not include input ${input}:\n` +
+                    translationData[block]
+                );
+            } catch (err) {
+                numLocaleErrors++;
+                console.error(err.message + '\n'); // eslint-disable-line no-console
+            }
+        }
+    }
+
+    if (numLocaleErrors > 0) {
+        numTotalErrors += numLocaleErrors;
+        throw new Error(`${numLocaleErrors} total error(s) for locale '${locale}'`);
+    }
+};
+
+const validate = (locale, callback) => {
+    fs.readFile(`${JSON_DIR}/${locale}.json`, function (err, data) {
+        if (err) callback(err);
+        // let this throw an error if invalid json
+        data = JSON.parse(data);
+
+        try {
+            validateExtensionInputs(data, locale);
+        } catch (error) {
+            console.error(error.message + '\n'); // eslint-disable-line no-console
+        }
+
+        callback();
+    });
+};
+
+async.each(Object.keys(locales), validate, function (err) {
+    if (err) {
+        console.error(err); // eslint-disable-line no-console
+        process.exit(1);
+    }
+
+    if (numTotalErrors > 0) {
+        console.error(`${numTotalErrors} total extension input error(s)`); // eslint-disable-line no-console
+        process.exit(1);
+    }
+});