diff --git a/client/modules/datafiles/src/projects/forms/BaseProjectForm.tsx b/client/modules/datafiles/src/projects/forms/BaseProjectForm.tsx
index b7ead8c7b2..1cf7517328 100644
--- a/client/modules/datafiles/src/projects/forms/BaseProjectForm.tsx
+++ b/client/modules/datafiles/src/projects/forms/BaseProjectForm.tsx
@@ -281,7 +281,11 @@ export const BaseProjectForm: React.FC<{
             ]}
             className="inner-form-item"
           >
-            <UserSelect userRole="pi" maxCount={1} />
+            <UserSelect
+              userRole="pi"
+              maxCount={1}
+              existingUsers={watchedUsers}
+            />
           </Form.Item>
         </Form.Item>
         <Form.Item
@@ -292,7 +296,7 @@ export const BaseProjectForm: React.FC<{
           <br />
           <br />
           <Form.Item name="coPis" initialValue={[]} className="inner-form-item">
-            <UserSelect userRole="co_pi" />
+            <UserSelect userRole="co_pi" existingUsers={watchedUsers} />
           </Form.Item>
         </Form.Item>
       </div>
@@ -305,7 +309,7 @@ export const BaseProjectForm: React.FC<{
           initialValue={[]}
           className="inner-form-item"
         >
-          <UserSelect userRole="team_member" />
+          <UserSelect userRole="team_member" existingUsers={watchedUsers} />
         </Form.Item>
       </Form.Item>
 
diff --git a/client/modules/datafiles/src/projects/forms/CreateProjectForm.tsx b/client/modules/datafiles/src/projects/forms/CreateProjectForm.tsx
index 4a7ac685df..18acee6e6c 100644
--- a/client/modules/datafiles/src/projects/forms/CreateProjectForm.tsx
+++ b/client/modules/datafiles/src/projects/forms/CreateProjectForm.tsx
@@ -1,5 +1,5 @@
 import { Button, Form, Input } from 'antd';
-import React, { useEffect } from 'react';
+import React, { useEffect, useMemo } from 'react';
 
 import { UserSelect, GuestMembersInput } from './_fields';
 import { TProjectUser } from './_fields/UserSelect';
@@ -34,6 +34,22 @@ export const BaseProjectCreateForm: React.FC<{
     ]);
   }, [form, user]);
 
+  const watchedPi = Form.useWatch(['pi'], form);
+  const watchedCoPis = Form.useWatch(['coPis'], form);
+  const watchedMembers = Form.useWatch(['teamMembers'], form);
+  const watchedGuestMembers = Form.useWatch(['guestMembers'], form);
+  const watchedUsers = useMemo(
+    () => [
+      ...(watchedPi ?? []),
+      ...(watchedCoPis ?? []),
+      ...(watchedMembers ?? []),
+      ...(watchedGuestMembers?.filter(
+        (f: TProjectUser) => !!f && f.fname && f.lname && f.email && f.inst
+      ) ?? []),
+    ],
+    [watchedPi, watchedCoPis, watchedMembers, watchedGuestMembers]
+  );
+
   if (!user) return null;
   return (
     <Form
@@ -94,7 +110,7 @@ export const BaseProjectCreateForm: React.FC<{
           <br />
           <br />
           <Form.Item name="coPis" initialValue={[]} className="inner-form-item">
-            <UserSelect userRole="co_pi" />
+            <UserSelect userRole="co_pi" existingUsers={watchedUsers} />
           </Form.Item>
         </Form.Item>
       </div>
@@ -106,7 +122,7 @@ export const BaseProjectCreateForm: React.FC<{
           initialValue={[]}
           className="inner-form-item"
         >
-          <UserSelect userRole="team_member" />
+          <UserSelect userRole="team_member" existingUsers={watchedUsers} />
         </Form.Item>
       </Form.Item>
 
diff --git a/client/modules/datafiles/src/projects/forms/_fields/AuthorSelect.tsx b/client/modules/datafiles/src/projects/forms/_fields/AuthorSelect.tsx
index d6dee50c30..541e16784e 100644
--- a/client/modules/datafiles/src/projects/forms/_fields/AuthorSelect.tsx
+++ b/client/modules/datafiles/src/projects/forms/_fields/AuthorSelect.tsx
@@ -16,7 +16,8 @@ export const AuthorSelect: React.FC<{
           (u) =>
             (u.email || '') === (a.email || '') &&
             u.fname === a.fname &&
-            u.lname === a.lname
+            u.lname === a.lname &&
+            (u.role || '') === (a.role || '')
         )
       )
       .filter((u) => !!u);
@@ -28,7 +29,8 @@ export const AuthorSelect: React.FC<{
             (a) =>
               (u.email || '') === (a.email || '') &&
               u.fname === a.fname &&
-              u.lname === a.lname
+              u.lname === a.lname &&
+              (u.role || '') === (a.role || '')
           )
       )
       .filter((u) => !!u);
@@ -60,7 +62,8 @@ export const AuthorSelect: React.FC<{
             (v) =>
               (user?.email || '') === (v.email || '') &&
               user?.fname === v.fname &&
-              user?.lname === v.lname
+              user?.lname === v.lname &&
+              (user?.role || '') === (v?.role || '')
           )
         )
         .map((v) => JSON.stringify(v) ?? [])}
diff --git a/client/modules/datafiles/src/projects/forms/_fields/UserSelect.tsx b/client/modules/datafiles/src/projects/forms/_fields/UserSelect.tsx
index b1958ba8d8..445c685111 100644
--- a/client/modules/datafiles/src/projects/forms/_fields/UserSelect.tsx
+++ b/client/modules/datafiles/src/projects/forms/_fields/UserSelect.tsx
@@ -18,7 +18,12 @@ export const UserSelect: React.FC<{
   userRole?: string;
   maxCount?: number;
   disabled?: boolean;
-}> = ({ value, onChange, id, userRole, maxCount, disabled }) => {
+  existingUsers?: TProjectUser[];
+}> = ({ value, onChange, id, userRole, maxCount, disabled, existingUsers }) => {
+  const existingUsernames = useMemo(
+    () => (existingUsers ?? []).map((u) => u.username),
+    [existingUsers]
+  );
   const initialOptions: SelectProps['options'] = useMemo(
     () =>
       value?.map((u) => ({
@@ -46,15 +51,17 @@ export const UserSelect: React.FC<{
         signal: controller.signal,
       })
       .then((resp) =>
-        resp.data.result.map((u) => ({
-          label: `${u.fname} ${u.lname} (${u.email})`,
-          value: JSON.stringify({ ...u, role: userRole }),
-        }))
+        resp.data.result
+          .filter((u) => !existingUsernames.includes(u.username))
+          .map((u) => ({
+            label: `${u.fname} ${u.lname} (${u.email})`,
+            value: JSON.stringify({ ...u, role: userRole }),
+          }))
       )
       .then((opts) => setData(opts))
       .catch((_) => setData([]));
     return () => controller.abort();
-  }, [debouncedSearchTerm, setData, userRole]);
+  }, [debouncedSearchTerm, setData, userRole, existingUsernames]);
 
   const changeCallback = (newValue: string[]) => {
     onChange && onChange(newValue.map((v) => JSON.parse(v)));