diff --git a/public/language/en-GB/topic.json b/public/language/en-GB/topic.json
index 7cae6bfcd4..f736000fb9 100644
--- a/public/language/en-GB/topic.json
+++ b/public/language/en-GB/topic.json
@@ -184,10 +184,13 @@
 	"topic-id": "Topic ID",
 	"move-posts-instruction": "Click the posts you want to move then enter a topic ID or go to the target topic",
 	"move-topic-instruction": "Select the target category and then click move",
-	"crosspost-topic-instruction": "Select one or more categories to cross-post to. Topic(s) will be accessible from the original category and all cross-posted categories.",
 	"change-owner-instruction": "Click the posts you want to assign to another user",
 	"manage-editors-instruction": "Manage the users who can edit this post below.",
 
+	"crossposts.instructions": "Select one or more categories to cross-post to. Topic(s) will be accessible from the original category and all cross-posted categories.",
+	"crossposts.listing": "This topic has been cross-posted to the following local categories:",
+	"crossposts.none": "This topic has not been cross-posted to any additional categories",
+
 	"composer.title-placeholder": "Enter your topic title here...",
 	"composer.handle-placeholder": "Enter your name/handle here",
 	"composer.hide": "Hide",
diff --git a/public/src/client/topic.js b/public/src/client/topic.js
index 97787e749e..b54185bf80 100644
--- a/public/src/client/topic.js
+++ b/public/src/client/topic.js
@@ -414,7 +414,6 @@ define('forum/topic', [
 				const { crossposts } = ajaxify.data;
 				const html = await app.parseAndTranslate('modals/crossposts', { crossposts });
 				bootbox.dialog({
-					size: 'sm',
 					onEscape: true,
 					backdrop: true,
 					title: '[[global:crossposts]]',
diff --git a/public/src/client/topic/crosspost.js b/public/src/client/topic/crosspost.js
new file mode 100644
index 0000000000..5c59eb855b
--- /dev/null
+++ b/public/src/client/topic/crosspost.js
@@ -0,0 +1,126 @@
+'use strict';
+
+
+define('forum/topic/crosspost', [
+	'categoryFilter', 'alerts', 'hooks', 'api', 'components',
+], function (categoryFilter, alerts, hooks, api, components) {
+	const Crosspost = {};
+	let modal;
+	let selectedCids;
+
+	Crosspost.init = function (tid) {
+		if (modal) {
+			return;
+		}
+		Crosspost.tid = tid;
+		Crosspost.cid = ajaxify.data.cid;
+		Crosspost.current = ajaxify.data.crossposts;
+
+		showModal();
+	};
+
+	function showModal() {
+		app.parseAndTranslate('modals/crosspost-topic', {
+			selectedCategory: ajaxify.data.crossposts.length ?
+				{
+					icon: 'fa-plus',
+					name: '[[unread:multiple-categories-selected]]',
+					bgColor: '#ddd',
+				} :
+				ajaxify.data.category,
+		}, function (html) {
+			modal = html;
+			$('body').append(modal);
+
+			const dropdownEl = modal.find('[component="category-selector"]');
+			dropdownEl.addClass('dropup');
+
+			categoryFilter.init($('[component="category/dropdown"]'), {
+				privilege: 'moderate',
+				onHidden: onCategoriesSelected,
+				hideAll: true,
+				hideUncategorized: true,
+				localOnly: true,
+				selectedCids: Array.from(new Set([ajaxify.data.cid, ...ajaxify.data.crossposts.map(c => c.cid)])),
+			});
+
+			modal.find('#crosspost_thread_commit').on('click', onCommitClicked);
+			modal.find('#crosspost_topic_cancel').on('click', closeCrosspostModal);
+		});
+	}
+
+	function onCategoriesSelected(data) {
+		({ selectedCids } = data);
+		console.log('changed? ', data.changed);
+		if (data.changed) {
+			modal.find('#crosspost_thread_commit').prop('disabled', false);
+		}
+	}
+
+	function onCommitClicked() {
+		const commitEl = modal.find('#crosspost_thread_commit');
+
+		if (!commitEl.prop('disabled') && selectedCids && selectedCids.length) {
+			commitEl.prop('disabled', true);
+			const data = {
+				tid: Crosspost.tid,
+				cids: selectedCids,
+			};
+
+			// TODO
+			// if (config.undoTimeout > 0) {
+			// 	return alerts.alert({
+			// 		alert_id: 'tids_move_' + (Crosspost.tid ? Crosspost.tid.join('-') : 'all'),
+			// 		title: '[[topic:thread-tools.move]]',
+			// 		message: message,
+			// 		type: 'success',
+			// 		timeout: config.undoTimeout,
+			// 		timeoutfn: function () {
+			// 			moveTopics(data);
+			// 		},
+			// 		clickfn: function (alert, params) {
+			// 			delete params.timeoutfn;
+			// 			alerts.success('[[topic:topic-move-undone]]');
+			// 		},
+			// 	});
+			// }
+
+			crosspost(data);
+		}
+	}
+
+	function crosspost(data) {
+		hooks.fire('action:topic.crosspost', data);
+
+		const cids = data.cids.map((cid) => parseInt(cid, 10));
+		if (!cids.includes(Crosspost.cid)) {
+			cids.unshift(Crosspost.cid);
+		}
+		const current = [Crosspost.cid, ...Crosspost.current.map(x => parseInt(x.cid, 10))];
+		const add = cids.filter(cid => !current.includes(cid));
+		const remove = current.filter(cid => !cids.includes(cid));
+
+		const queries = [
+			...add.map((cid) => { return api.post(`/topics/${data.tid}/crossposts`, { cid }); }),
+			...remove.map((cid) => { return api.del(`/topics/${data.tid}/crossposts`, { cid }); }),
+		];
+
+		Promise.all(queries).then(async () => {
+			const statsEl = components.get('topic/stats');
+			const { crossposts } = await api.get(`/topics/${data.tid}/crossposts`);
+			ajaxify.data.crossposts = crossposts;
+			const html = await app.parseAndTranslate('partials/topic/stats', ajaxify.data);
+			statsEl.html(html);
+			closeCrosspostModal();
+		}).catch(alerts.error);
+	}
+
+	function closeCrosspostModal() {
+		if (modal) {
+			modal.remove();
+			modal = null;
+		}
+	}
+
+	return Crosspost;
+});
diff --git a/src/views/modals/crosspost-topic.tpl b/src/views/modals/crosspost-topic.tpl
index a7ae3be3ea..bb95e8e329 100644
--- a/src/views/modals/crosspost-topic.tpl
+++ b/src/views/modals/crosspost-topic.tpl
@@ -4,7 +4,7 @@
 	</h5>
 	<div class="card-body">
 		<p>
-			[[topic:crosspost-topic-instruction]]
+			[[topic:crossposts.instructions]]
 		</p>
 		<!-- IMPORT partials/category/filter-dropdown-right.tpl -->
 	</div>
diff --git a/src/views/modals/crossposts.tpl b/src/views/modals/crossposts.tpl
new file mode 100644
index 0000000000..8b7d2b9272
--- /dev/null
+++ b/src/views/modals/crossposts.tpl
@@ -0,0 +1,10 @@
+<div class="mb-3">
+	{{{ if crossposts.length }}}
+		<p>[[topic:crossposts.listing]]</p>
+		{{{ each crossposts }}}
+		{buildCategoryLabel(./category, "a", "border")}
+		{{{ end }}}
+	{{{ else }}}
+		<p>[[topic:crossposts.none]]</p>
+	{{{ end }}}
+</div>