diff --git a/deposit/static/deposit/js/data.js b/deposit/static/deposit/js/data.js
index 719efe8a..a2b88e2d 100644
--- a/deposit/static/deposit/js/data.js
+++ b/deposit/static/deposit/js/data.js
@@ -237,6 +237,7 @@ $(function () {
     r.cancel()
     $('#files').html('')
     $('#uploads').addClass('hidden')
+    $('#unsupportedCharsWarning').addClass('hidden')
     // clear information present for next time dialog is presented
     $('.uploads-progress-information').html('')
     $('.uploads-total-progress-bar').css('width', '0%')
@@ -262,6 +263,11 @@ $(function () {
         const folderName = file.relativePath.substring(0, file.relativePath.indexOf('/'))
         let overwrite = false
 
+        const diamondQuestionMarkPattern = /\uFFFD/
+        if (diamondQuestionMarkPattern.test(file.name)) {
+          $('#unsupportedCharsWarning').removeClass('hidden')
+        }
+
         const $self = $('#' + file.uniqueIdentifier)
         // Pause btn
         $self.find('.upload-pause').on('click', function () {
diff --git a/deposit/templates/deposit/data.html b/deposit/templates/deposit/data.html
index abb0b3ec..6497fea9 100644
--- a/deposit/templates/deposit/data.html
+++ b/deposit/templates/deposit/data.html
@@ -45,6 +45,9 @@ <h5 class="modal-title">Uploads
                 <button type="button" class="btn-close btn-close-uploads-overview" data-bs-dismiss="modal" aria-label="Close" title="Close"></button>
             </div>
             <div class="modal-body">
+                <div id="unsupportedCharsWarning" class="hidden alert alert-primary">
+                    Uploaded filenames contain unsupported characters and are renamed for compatibility.
+                </div>
                 <div id="files"></div>
             </div>
             <div class="modal-footer">