diff --git a/Source/Core/DolphinQt/Debugger/MemoryWidget.cpp b/Source/Core/DolphinQt/Debugger/MemoryWidget.cpp
index 4c15e92a03..b4ef33fbe5 100644
--- a/Source/Core/DolphinQt/Debugger/MemoryWidget.cpp
+++ b/Source/Core/DolphinQt/Debugger/MemoryWidget.cpp
@@ -618,12 +618,26 @@ void MemoryWidget::ValidateAndPreviewInputValue()
   if (input_type != Type::ASCII)
     input_text.remove(QLatin1Char(' '));
 
-  if (m_base_check->isChecked())
+  if (input_type == Type::HexString)
   {
+    // Hex strings are parsed using QByteArray::fromHex which doesn't expect a 0x prefix. If the
+    // user has inserted one, remove it.
+    if (input_text.startsWith(QStringLiteral("0x"), Qt::CaseInsensitive))
+      input_text.remove(0, 2);
+  }
+  else if (m_base_check->isChecked())
+  {
+    // Add 0x to the front of the input (after the '-', if present), but only if the user didn't
+    // already do so.
     if (input_text.startsWith(QLatin1Char('-')))
-      input_text.insert(1, QStringLiteral("0x"));
-    else
+    {
+      if (!input_text.startsWith(QStringLiteral("-0x"), Qt::CaseInsensitive))
+        input_text.insert(1, QStringLiteral("0x"));
+    }
+    else if (!input_text.startsWith(QStringLiteral("0x"), Qt::CaseInsensitive))
+    {
       input_text.prepend(QStringLiteral("0x"));
+    }
   }
 
   QFont font;