diff --git a/addons/mail/static/src/components/attachment/attachment.xml b/addons/mail/static/src/components/attachment/attachment.xml
index 8af00288b8b..7be59392838 100644
--- a/addons/mail/static/src/components/attachment/attachment.xml
+++ b/addons/mail/static/src/components/attachment/attachment.xml
@@ -39,7 +39,7 @@
                             </div>
                             <div class="o_Attachment_actions">
                                 <!-- Remove button -->
-                                <t t-if="props.isEditable and !attachment.isTemporary" t-key="'unlink'">
+                                <t t-if="props.isEditable" t-key="'unlink'">
                                     <div class="o_Attachment_action o_Attachment_actionUnlink"
                                         t-att-class="{
                                             'o-pretty': attachment.isLinkedToComposer,
@@ -75,7 +75,7 @@
                 </t>
                 <!-- Attachment aside -->
                 <t t-if="detailsMode !== 'hover' and (props.isDownloadable or props.isEditable)">
-                    <div class="o_Attachment_aside" t-att-class="{ 'o-has-multiple-action': !attachment.isTemporary and props.isDownloadable and props.isEditable }">
+                    <div class="o_Attachment_aside" t-att-class="{ 'o-has-multiple-action': props.isDownloadable and props.isEditable }">
                         <!-- Uploading icon -->
                         <t t-if="attachment.isTemporary and attachment.isLinkedToComposer">
                             <div class="o_Attachment_asideItem o_Attachment_asideItemUploading" title="Uploading">
@@ -89,7 +89,7 @@
                             </div>
                         </t>
                         <!-- Remove button -->
-                        <t t-if="props.isEditable and !attachment.isTemporary">
+                        <t t-if="props.isEditable">
                             <div class="o_Attachment_asideItem o_Attachment_asideItemUnlink" t-att-class="{ 'o-pretty': attachment.isLinkedToComposer }" t-on-click="_onClickUnlink" title="Remove">
                                 <i class="fa fa-times"/>
                             </div>
diff --git a/addons/mail/static/src/components/composer/composer_tests.js b/addons/mail/static/src/components/composer/composer_tests.js
index 5d337e0ed0c..459e0d2c799 100644
--- a/addons/mail/static/src/components/composer/composer_tests.js
+++ b/addons/mail/static/src/components/composer/composer_tests.js
@@ -40,9 +40,10 @@ QUnit.module('composer_tests.js', {
         };
 
         this.start = async params => {
-            const { env, widget } = await start(Object.assign({}, params, {
+            const { afterEvent, env, widget } = await start(Object.assign({}, params, {
                 data: this.data,
             }));
+            this.afterEvent = afterEvent;
             this.env = env;
             this.widget = widget;
         };
@@ -1141,6 +1142,102 @@ QUnit.test('warning on send with shortcut when attempting to post message with s
     );
 });
 
+QUnit.test('remove an uploading attachment', async function (assert) {
+    assert.expect(4);
+
+    await this.start({
+        async mockFetch(resource, init) {
+            const res = this._super(...arguments);
+            if (resource === '/web/binary/upload_attachment') {
+                // simulates uploading indefinitely
+                await new Promise(() => {});
+            }
+            return res;
+        }
+    });
+    const composer = this.env.models['mail.composer'].create();
+    await this.createComposerComponent(composer);
+    const file = await createFile({
+        content: 'hello, world',
+        contentType: 'text/plain',
+        name: 'text.txt',
+    });
+    await afterNextRender(() =>
+        inputFiles(
+            document.querySelector('.o_FileUploader_input'),
+            [file]
+        )
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Composer_attachmentList',
+        "should have an attachment list"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Composer .o_Attachment',
+        "should have only one attachment"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Composer .o_Attachment.o-temporary',
+        "should have an uploading attachment"
+    );
+
+    await afterNextRender(() =>
+        document.querySelector('.o_Attachment_asideItemUnlink').click());
+    assert.containsNone(
+        document.body,
+        '.o_Composer .o_Attachment',
+        "should not have any attachment left after unlinking temporary one"
+    );
+});
+
+QUnit.test('remove an uploading attachment aborts upload', async function (assert) {
+    assert.expect(1);
+
+    await this.start({
+        async mockFetch(resource, init) {
+            const res = this._super(...arguments);
+            if (resource === '/web/binary/upload_attachment') {
+                // simulates uploading indefinitely
+                await new Promise(() => {});
+            }
+            return res;
+        }
+    });
+    const composer = this.env.models['mail.composer'].create();
+    await this.createComposerComponent(composer);
+    const file = await createFile({
+        content: 'hello, world',
+        contentType: 'text/plain',
+        name: 'text.txt',
+    });
+    await afterNextRender(() =>
+        inputFiles(
+            document.querySelector('.o_FileUploader_input'),
+            [file]
+        )
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Attachment',
+        "should contain an attachment"
+    );
+    const attachmentLocalId = document.querySelector('.o_Attachment').dataset.attachmentLocalId;
+
+    await this.afterEvent({
+        eventName: 'o-attachment-upload-abort',
+        func: () => {
+            document.querySelector('.o_Attachment_asideItemUnlink').click();
+        },
+        message: "attachment upload request should have been aborted",
+        predicate: ({ attachment }) => {
+            return attachment.localId === attachmentLocalId;
+        },
+    });
+});
+
 });
 });
 });
diff --git a/addons/mail/static/src/components/file_uploader/file_uploader.js b/addons/mail/static/src/components/file_uploader/file_uploader.js
index a8f2fb9cf68..efa0026842d 100644
--- a/addons/mail/static/src/components/file_uploader/file_uploader.js
+++ b/addons/mail/static/src/components/file_uploader/file_uploader.js
@@ -97,14 +97,26 @@ class FileUploader extends Component {
      */
     async _performUpload(files) {
         for (const file of files) {
-            const response = await this.env.browser.fetch('/web/binary/upload_attachment', {
-                method: 'POST',
-                body: this._createFormData(file),
-            });
-            let html = await response.text();
-            const template = document.createElement('template');
-            template.innerHTML = html.trim();
-            window.eval(template.content.firstChild.textContent);
+            const uploadingAttachment = this.env.models['mail.attachment'].find(attachment =>
+                attachment.isTemporary &&
+                attachment.filename === file.name
+            );
+
+            try {
+                const response = await this.env.browser.fetch('/web/binary/upload_attachment', {
+                    method: 'POST',
+                    body: this._createFormData(file),
+                    signal: uploadingAttachment.uploadingAbortController.signal,
+                });
+                let html = await response.text();
+                const template = document.createElement('template');
+                template.innerHTML = html.trim();
+                window.eval(template.content.firstChild.textContent);
+            } catch (e) {
+                if (e.name !== 'AbortError') {
+                    throw e;
+                }
+            }
         }
     }
 
diff --git a/addons/mail/static/src/models/attachment/attachment.js b/addons/mail/static/src/models/attachment/attachment.js
index a9adce2579f..77ebf667db0 100644
--- a/addons/mail/static/src/models/attachment/attachment.js
+++ b/addons/mail/static/src/models/attachment/attachment.js
@@ -96,11 +96,15 @@ function factory(dependencies) {
          * Remove this attachment globally.
          */
         async remove() {
-            await this.async(() => this.env.services.rpc({
-                model: 'ir.attachment',
-                method: 'unlink',
-                args: [this.id],
-            }, { shadow: true }));
+            if (!this.isTemporary) {
+                await this.async(() => this.env.services.rpc({
+                    model: 'ir.attachment',
+                    method: 'unlink',
+                    args: [this.id],
+                }, { shadow: true }));
+            } else if (this.uploadingAbortController) {
+                this.uploadingAbortController.abort();
+            }
             this.delete();
         }
 
@@ -246,6 +250,25 @@ function factory(dependencies) {
             return this.mimetype && this.mimetype.split('/').shift();
         }
 
+        /**
+         * @private
+         * @returns {AbortController|undefined}
+         */
+        _computeUploadingAbortController() {
+            if (this.isTemporary) {
+                if (!this.uploadingAbortController) {
+                    const abortController = new AbortController();
+                    abortController.signal.onabort = () => {
+                        this.env.messagingBus.trigger('o-attachment-upload-abort', {
+                            attachment: this
+                        });
+                    };
+                    return abortController;
+                }
+                return this.uploadingAbortController;
+            }
+            return undefined;
+        }
     }
 
     Attachment.fields = {
@@ -328,6 +351,17 @@ function factory(dependencies) {
             inverse: 'attachments',
         }),
         type: attr(),
+        /**
+         * Abort Controller linked to the uploading process of this attachment.
+         * Useful in order to cancel the in-progress uploading of this attachment.
+         */
+        uploadingAbortController: attr({
+            compute: '_computeUploadingAbortController',
+            dependencies: [
+                'isTemporary',
+                'uploadingAbortController',
+            ],
+        }),
         url: attr(),
     };