diff --git a/app/main/views/uploads.py b/app/main/views/uploads.py
index 052329766..6a2315a90 100644
--- a/app/main/views/uploads.py
+++ b/app/main/views/uploads.py
@@ -1,7 +1,16 @@
 import uuid
 from io import BytesIO
 
-from flask import flash, redirect, render_template, request, url_for
+from flask import (
+    current_app,
+    flash,
+    redirect,
+    render_template,
+    request,
+    url_for,
+)
+from notifications_utils.pdf import pdf_page_count
+from PyPDF2.utils import PdfReadError
 
 from app import current_service
 from app.extensions import antivirus_client
@@ -28,12 +37,16 @@ def upload_letter(service_id):
 
         virus_free = antivirus_client.scan(BytesIO(pdf_file_bytes))
         if not virus_free:
-            flash('Your file has failed the virus check', 'dangerous')
-            return render_template('views/uploads/choose-file.html', form=form), 400
+            return invalid_upload_error('Your file has failed the virus check')
 
         if len(pdf_file_bytes) > MAX_FILE_UPLOAD_SIZE:
-            flash('Your file must be smaller than 2MB', 'dangerous')
-            return render_template('views/uploads/choose-file.html', form=form), 400
+            return invalid_upload_error('Your file must be smaller than 2MB')
+
+        try:
+            pdf_page_count(BytesIO(pdf_file_bytes))
+        except PdfReadError:
+            current_app.logger.info('Invalid PDF uploaded for service_id: {}'.format(service_id))
+            return invalid_upload_error('Your file must be a valid PDF')
 
         upload_id = uuid.uuid4()
 
@@ -49,6 +62,11 @@ def upload_letter(service_id):
     return render_template('views/uploads/choose-file.html', form=form)
 
 
+def invalid_upload_error(message):
+    flash(message, 'dangerous')
+    return render_template('views/uploads/choose-file.html', form=PDFUploadForm()), 400
+
+
 @main.route("/services/<service_id>/preview-letter/<file_id>")
 @user_has_permissions('send_messages')
 def uploaded_letter_preview(service_id, file_id):
diff --git a/tests/app/main/views/test_uploads.py b/tests/app/main/views/test_uploads.py
index 530130e74..d8daf1398 100644
--- a/tests/app/main/views/test_uploads.py
+++ b/tests/app/main/views/test_uploads.py
@@ -90,6 +90,20 @@ def test_post_choose_upload_file_when_file_is_too_big(mocker, client_request):
     assert normalize_spaces(page.select('.banner-dangerous')[0].text) == 'Your file must be smaller than 2MB'
 
 
+def test_post_choose_upload_file_when_file_is_malformed(mocker, client_request):
+    mocker.patch('app.main.views.uploads.antivirus_client.scan', return_value=True)
+
+    with open('tests/test_pdf_files/no_eof_marker.pdf', 'rb') as file:
+        page = client_request.post(
+            'main.upload_letter',
+            service_id=SERVICE_ONE_ID,
+            _data={'file': file},
+            _expected_status=400
+        )
+    assert page.find('h1').text == 'Upload a letter'
+    assert normalize_spaces(page.select('.banner-dangerous')[0].text) == 'Your file must be a valid PDF'
+
+
 def test_uploaded_letter_preview(client_request):
     page = client_request.get(
         'main.uploaded_letter_preview',
diff --git a/tests/test_pdf_files/no_eof_marker.pdf b/tests/test_pdf_files/no_eof_marker.pdf
new file mode 100644
index 000000000..857ae1fbf
Binary files /dev/null and b/tests/test_pdf_files/no_eof_marker.pdf differ