diff --git a/src/core/operations/UnescapeUnicodeCharacters.mjs b/src/core/operations/UnescapeUnicodeCharacters.mjs
index 02d16662d3..f7759c7849 100644
--- a/src/core/operations/UnescapeUnicodeCharacters.mjs
+++ b/src/core/operations/UnescapeUnicodeCharacters.mjs
@@ -56,7 +56,8 @@ class UnescapeUnicodeCharacters extends Operation {
      */
     run(input, args) {
         const prefix = prefixToRegex[args[0]],
-            regex = new RegExp(prefix+"([a-f\\d]{4})", "ig");
+            quantifier = args[0] === "U+" ? "{4,6}" : "{4}",
+            regex = new RegExp(prefix+"([a-f\\d]"+quantifier+")", "ig");
         let output = "",
             m,
             i = 0;
diff --git a/tests/operations/index.mjs b/tests/operations/index.mjs
index f030349d2a..66f8f26999 100644
--- a/tests/operations/index.mjs
+++ b/tests/operations/index.mjs
@@ -174,6 +174,7 @@ import "./tests/ToFromInsensitiveRegex.mjs";
 import "./tests/TranslateDateTimeFormat.mjs";
 import "./tests/Typex.mjs";
 import "./tests/UnescapeString.mjs";
+import "./tests/UnescapeUnicodeCharacters.mjs";
 import "./tests/Unicode.mjs";
 import "./tests/URLEncodeDecode.mjs";
 import "./tests/RSA.mjs";
diff --git a/tests/operations/tests/UnescapeUnicodeCharacters.mjs b/tests/operations/tests/UnescapeUnicodeCharacters.mjs
new file mode 100644
index 0000000000..99955e04b4
--- /dev/null
+++ b/tests/operations/tests/UnescapeUnicodeCharacters.mjs
@@ -0,0 +1,88 @@
+/**
+ * Unescape Unicode Characters operation tests.
+ *
+ * @author williballenthin
+ * @copyright Crown Copyright 2024
+ * @license Apache-2.0
+ */
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        name: "Unescape Unicode Characters: \\u 4-digit BMP",
+        input: "\\u03c3\\u03bf\\u03c5",
+        expectedOutput: "σου",
+        recipeConfig: [
+            {
+                op: "Unescape Unicode Characters",
+                args: ["\\u"],
+            },
+        ],
+    },
+    {
+        name: "Unescape Unicode Characters: %u 4-digit BMP",
+        input: "%u03c3%u03bf%u03c5",
+        expectedOutput: "σου",
+        recipeConfig: [
+            {
+                op: "Unescape Unicode Characters",
+                args: ["%u"],
+            },
+        ],
+    },
+    {
+        name: "Unescape Unicode Characters: U+ 4-digit BMP",
+        input: "U+0041",
+        expectedOutput: "A",
+        recipeConfig: [
+            {
+                op: "Unescape Unicode Characters",
+                args: ["U+"],
+            },
+        ],
+    },
+    {
+        name: "Unescape Unicode Characters: U+ 5-digit astral plane emoji",
+        input: "U+1F600",
+        expectedOutput: "\u{1F600}",
+        recipeConfig: [
+            {
+                op: "Unescape Unicode Characters",
+                args: ["U+"],
+            },
+        ],
+    },
+    {
+        name: "Unescape Unicode Characters: U+ 6-digit zero-padded",
+        input: "U+000041",
+        expectedOutput: "A",
+        recipeConfig: [
+            {
+                op: "Unescape Unicode Characters",
+                args: ["U+"],
+            },
+        ],
+    },
+    {
+        name: "Unescape Unicode Characters: U+ mixed lengths",
+        input: "U+0041 U+1F600 U+000042",
+        expectedOutput: "A \u{1F600} B",
+        recipeConfig: [
+            {
+                op: "Unescape Unicode Characters",
+                args: ["U+"],
+            },
+        ],
+    },
+    {
+        name: "Unescape Unicode Characters: passthrough with no matches",
+        input: "hello world",
+        expectedOutput: "hello world",
+        recipeConfig: [
+            {
+                op: "Unescape Unicode Characters",
+                args: ["\\u"],
+            },
+        ],
+    },
+]);