diff --git a/client/i18n/locales/english/translations.json b/client/i18n/locales/english/translations.json
index 4261e671f6..a615c39087 100644
--- a/client/i18n/locales/english/translations.json
+++ b/client/i18n/locales/english/translations.json
@@ -102,6 +102,7 @@
       "contains invalid characters": "Username \"{{username}}\" contains invalid characters",
       "is too short": "Username \"{{username}}\" is too short",
       "is a reserved error code": "Username \"{{username}}\" is a reserved error code",
+      "must be lowercase": "Username \"{{username}}\" must be lowercase",
       "unavailable": "Username not available",
       "validating": "Validating username...",
       "available": "Username is available",
diff --git a/client/src/components/settings/Username.js b/client/src/components/settings/Username.js
index a5f3280bb1..0c7e95838e 100644
--- a/client/src/components/settings/Username.js
+++ b/client/src/components/settings/Username.js
@@ -98,7 +98,7 @@ class UsernameSettings extends Component {
   handleChange(e) {
     e.preventDefault();
     const { username, validateUsername } = this.props;
-    const newValue = e.target.value.toLowerCase();
+    const newValue = e.target.value;
     return this.setState(
       {
         formValue: newValue,
diff --git a/cypress/integration/settings/username-change.js b/cypress/integration/settings/username-change.js
index b8ad6347bc..2db0a49ea9 100644
--- a/cypress/integration/settings/username-change.js
+++ b/cypress/integration/settings/username-change.js
@@ -121,7 +121,7 @@ describe('Username input field', () => {
       .clear({ force: true })
       .type('Quincy Larson', { force: true });
 
-    cy.contains('Username "quincy larson" contains invalid characters')
+    cy.contains('Username "Quincy Larson" contains invalid characters')
       .should('be.visible')
       .should('have.attr', 'role', 'alert')
       // We are checking for classes here to check for proper styling
@@ -198,4 +198,22 @@ describe('Username input field', () => {
 
     cy.resetUsername();
   });
+  it('Should show warning if username includes uppercase characters', () => {
+    cy.get('@usernameInput')
+      .clear({ force: true })
+      .type('QuincyLarson', { force: true });
+
+    cy.contains('Username "QuincyLarson" must be lowercase')
+      .should('be.visible')
+      .should('have.attr', 'role', 'alert')
+      .should('have.class', 'alert alert-danger');
+  });
+
+  it('Should not be able to click the `Save` button if username includes uppercase characters', () => {
+    cy.get('@usernameInput')
+      .clear({ force: true })
+      .type('QuincyLarson', { force: true });
+
+    cy.get('@usernameForm').contains('Save').should('be.disabled');
+  });
 });
diff --git a/utils/validate.js b/utils/validate.js
index 0ed4af896b..d604c41ab6 100644
--- a/utils/validate.js
+++ b/utils/validate.js
@@ -8,15 +8,20 @@ const usernameIsHttpStatusCode = {
   valid: false,
   error: 'is a reserved error code'
 };
+const usernameUpperCase = { valid: false, error: 'must be lowercase' };
 
 const isNumeric = num => !isNaN(num);
 const validCharsRE = /^[a-zA-Z0-9\-_+]*$/;
 const isHttpStatusCode = str =>
   isNumeric(str) && parseInt(str, 10) >= 100 && parseInt(str, 10) <= 599;
+const isUsernameLowercase = str => {
+  return str === str.toLowerCase();
+};
 const isValidUsername = str => {
   if (!validCharsRE.test(str)) return invalidCharError;
   if (str.length < 3) return usernameTooShort;
   if (isHttpStatusCode(str)) return usernameIsHttpStatusCode;
+  if (!isUsernameLowercase(str)) return usernameUpperCase;
   return validationSuccess;
 };
 
@@ -24,8 +29,10 @@ module.exports = {
   isNumeric,
   isHttpStatusCode,
   isValidUsername,
+  isUsernameLowercase,
   validationSuccess,
   usernameTooShort,
   usernameIsHttpStatusCode,
-  invalidCharError
+  invalidCharError,
+  usernameUpperCase
 };
diff --git a/utils/validate.test.js b/utils/validate.test.js
index a96d8f8db5..f5c84f20e8 100644
--- a/utils/validate.test.js
+++ b/utils/validate.test.js
@@ -5,7 +5,8 @@ const {
   usernameTooShort,
   validationSuccess,
   usernameIsHttpStatusCode,
-  invalidCharError
+  invalidCharError,
+  usernameUpperCase
 } = require('./validate');
 
 function inRange(num, range) {
@@ -38,6 +39,9 @@ describe('isValidUsername', () => {
     expect(isValidUsername('a-b')).toStrictEqual(validationSuccess);
     expect(isValidUsername('a_b')).toStrictEqual(validationSuccess);
   });
+  it('rejects uppercase characters', () => {
+    expect(isValidUsername('Quincy')).toStrictEqual(usernameUpperCase);
+  });
 
   it('rejects all other ASCII characters', () => {
     const allowedCharactersList = ['-', '_', '+'];
@@ -52,7 +56,7 @@ describe('isValidUsername', () => {
       let expected = invalidCharError;
       if (allowedCharactersList.includes(char)) expected = validationSuccess;
       if (inRange(code, numbers)) expected = validationSuccess;
-      if (inRange(code, upperCase)) expected = validationSuccess;
+      if (inRange(code, upperCase)) expected = usernameUpperCase;
       if (inRange(code, lowerCase)) expected = validationSuccess;
       expect(isValidUsername(base + char)).toStrictEqual(expected);
     }