diff --git a/.changeset/shiny-keys-dream.md b/.changeset/shiny-keys-dream.md
new file mode 100644
index 0000000000..3e28f5d431
--- /dev/null
+++ b/.changeset/shiny-keys-dream.md
@@ -0,0 +1,6 @@
+---
+'@backstage/plugin-techdocs': patch
+---
+
+Set admonition font size to 1rem in TechDocs to align with the rest of the document's font sizes.
+Fixes #5448 and #5541.
diff --git a/plugins/techdocs/src/reader/components/Reader.tsx b/plugins/techdocs/src/reader/components/Reader.tsx
index 09cd3abec8..c779985364 100644
--- a/plugins/techdocs/src/reader/components/Reader.tsx
+++ b/plugins/techdocs/src/reader/components/Reader.tsx
@@ -183,21 +183,24 @@ export const Reader = ({ entityId, onReady }: Props) => {
           border-bottom: 1px solid ${theme.palette.text.primary};
         }
         .md-typeset table:not([class]) th { font-weight: bold; }
+        .md-typeset .admonition, .md-typeset details {
+          font-size: 1rem;
+        }
         @media screen and (max-width: 76.1875em) {
-          .md-nav { 
-            background-color: ${theme.palette.background.default}; 
+          .md-nav {
+            background-color: ${theme.palette.background.default};
             transition: none !important
           }
           .md-sidebar--secondary { display: none; }
           .md-sidebar--primary { left: 72px; width: 10rem }
           .md-content { margin-left: 10rem; max-width: calc(100% - 10rem); }
           .md-content__inner { font-size: 0.9rem }
-          .md-footer { 
-            position: static; 
-            margin-left: 10rem; 
-            width: calc(100% - 10rem); 
+          .md-footer {
+            position: static;
+            margin-left: 10rem;
+            width: calc(100% - 10rem);
           }
-          .md-nav--primary .md-nav__title {  
+          .md-nav--primary .md-nav__title {
             white-space: normal;
             height: auto;
             line-height: 1rem;