diff --git a/web/markdown/markdown-spoiler.react.js b/web/markdown/markdown-spoiler.react.js
--- a/web/markdown/markdown-spoiler.react.js
+++ b/web/markdown/markdown-spoiler.react.js
@@ -4,6 +4,8 @@
 
 import type { ReactElement } from 'lib/shared/markdown';
 
+import css from './markdown.css';
+
 type MarkdownSpoilerProps = {
   +text: ReactElement,
 };
@@ -11,7 +13,7 @@
 function MarkdownSpoiler(props: MarkdownSpoilerProps): React.Node {
   const { text } = props;
 
-  return <span>{text}</span>;
+  return <span className={css.spoiler}>{text}</span>;
 }
 
 const MemoizedMarkdownSpoiler: React.ComponentType<MarkdownSpoilerProps> = React.memo<MarkdownSpoilerProps>(
diff --git a/web/markdown/markdown.css b/web/markdown/markdown.css
--- a/web/markdown/markdown.css
+++ b/web/markdown/markdown.css
@@ -76,3 +76,9 @@
 div.darkBackground a {
   color: white;
 }
+
+span.spoiler {
+  background: var(--spoiler-background-color);
+  color: var(--spoiler-text-color);
+  cursor: pointer;
+}
diff --git a/web/theme.css b/web/theme.css
--- a/web/theme.css
+++ b/web/theme.css
@@ -181,4 +181,6 @@
   --compose-subchannel-mark-color: var(--violet-light-100);
   --enum-option-icon-color: var(--violet-dark-100);
   --show-password-bg-hover: var(--shades-black-70);
+  --spoiler-text-color: var(--shades-black-80);
+  --spoiler-background-color: var(--shades-black-80);
 }