diff --git a/core/autoload/fonts.el b/core/autoload/fonts.el
index 711828f0d..21636ca1d 100644
--- a/core/autoload/fonts.el
+++ b/core/autoload/fonts.el
@@ -32,6 +32,14 @@ acceptable values for this variable.")
   (or (x-decompose-font-name fontname)
       (error "Cannot decompose font name")))
 
+(defun doom--frame-list (&optional frame)
+  "Return a list consisting of FRAME and all of FRAME's child frames."
+  (let ((frame (or frame (selected-frame))))
+    (cons (selected-frame)
+          (cl-loop for fr in (frame-list)
+                   if (eq (frame-parameter fr 'parent-frame) frame)
+                   collect fr))))
+
 ;;;###autoload
 (defun doom-adjust-font-size (increment &optional frame)
   "Increase size of font in FRAME by INCREMENT.
@@ -52,7 +60,8 @@ Optional FRAME parameter defaults to current frame."
     (setq font (x-compose-font-name font))
     (unless (x-list-fonts font)
       (error "Cannot change font size"))
-    (modify-frame-parameters frame `((font . ,font)))))
+    (dolist (fr (doom--frame-list frame))
+      (modify-frame-parameters fr `((font . ,font))))))
 
 
 ;;
@@ -87,7 +96,7 @@ Assuming it has been adjusted via `doom/increase-font-size' and
   (let ((zoom-factor (frame-parameter nil 'font-scale)))
     (if (not zoom-factor)
         (user-error "Font size hasn't been changed")
-      (set-frame-font doom-font t)
+      (set-frame-font doom-font t (doom--frame-list))
       (modify-frame-parameters nil '((font-scale)))
       (run-hooks 'doom-change-font-size-hook))))
 
@@ -109,6 +118,6 @@ This uses `doom/increase-font-size' under the hood, and enlargens the font by
           (set-frame-font (if doom-big-font-mode doom-big-font doom-font)
                           t (list frame))
           (run-hooks 'doom-change-font-size-hook))
-      (set-frame-font doom-font t (list frame))
+      (set-frame-font doom-font t (doom--frame-list frame))
       (when doom-big-font-mode
         (doom-adjust-font-size doom-big-font-increment frame)))))