diff --git a/packages/global-styles-ui/src/font-library/upload-fonts.tsx b/packages/global-styles-ui/src/font-library/upload-fonts.tsx
index e9fb375f0c70c6..8b11439c510605 100644
--- a/packages/global-styles-ui/src/font-library/upload-fonts.tsx
+++ b/packages/global-styles-ui/src/font-library/upload-fonts.tsx
@@ -13,7 +13,6 @@ import {
 	ProgressBar,
 } from '@wordpress/components';
 import { useContext, useState } from '@wordpress/element';
-import type { FontFace } from '@wordpress/core-data';
 
 /**
  * Internal dependencies
@@ -22,7 +21,21 @@ import { ALLOWED_FILE_EXTENSIONS } from './utils/constants';
 import { FontLibraryContext } from './context';
 import { Font } from './lib/lib-font.browser';
 import makeFamiliesFromFaces from './utils/make-families-from-faces';
-import { loadFontFaceInBrowser } from './utils';
+import { loadFontFaceInBrowser, normalizeCSSFontFaceFontFamily } from './utils';
+
+export interface FontFaceMetadata {
+	/*
+	 * Font name for display
+	 */
+	name: string;
+
+	/**
+	 * CSS @font-face font-family value.
+	 */
+	fontFamily: string;
+	fontStyle?: string | undefined;
+	fontWeight?: string | number | undefined;
+}
 
 function UploadFonts() {
 	const { installFonts } = useContext( FontLibraryContext );
@@ -108,11 +121,7 @@ function UploadFonts() {
 		const fontFacesLoaded = await Promise.all(
 			files.map( async ( fontFile: File ) => {
 				const fontFaceData = await getFontFaceMetadata( fontFile );
-				await loadFontFaceInBrowser(
-					fontFaceData,
-					fontFaceData.file,
-					'all'
-				);
+				await loadFontFaceInBrowser( fontFaceData, fontFile, 'all' );
 				return fontFaceData;
 			} )
 		);
@@ -146,7 +155,9 @@ function UploadFonts() {
 		} );
 	}
 
-	const getFontFaceMetadata = async ( fontFile: File ) => {
+	const getFontFaceMetadata = async (
+		fontFile: File
+	): Promise< FontFaceMetadata > => {
 		const buffer = await readFileAsArrayBuffer( fontFile );
 		const fontObj: Font & {
 			onload?: ( val: { detail: { font: any } } ) => void;
@@ -171,9 +182,12 @@ function UploadFonts() {
 		const weightRange = weightAxis
 			? `${ weightAxis.minValue } ${ weightAxis.maxValue }`
 			: null;
+
+		const cssFontFamily = normalizeCSSFontFaceFontFamily( fontName );
+
 		return {
-			file: fontFile,
-			fontFamily: fontName,
+			name: fontName,
+			fontFamily: cssFontFamily,
 			fontStyle: isItalic ? 'italic' : 'normal',
 			fontWeight: weightRange || fontWeight,
 		};
@@ -185,7 +199,7 @@ function UploadFonts() {
 	 * @param {Array} fontFaces The font faces to be installed
 	 * @return {void}
 	 */
-	const handleInstall = async ( fontFaces: FontFace[] ) => {
+	const handleInstall = async ( fontFaces: FontFaceMetadata[] ) => {
 		const fontFamilies = makeFamiliesFromFaces( fontFaces );
 
 		try {
diff --git a/packages/global-styles-ui/src/font-library/utils/index.ts b/packages/global-styles-ui/src/font-library/utils/index.ts
index 8feddd77c44f4d..bdadbef0f947aa 100644
--- a/packages/global-styles-ui/src/font-library/utils/index.ts
+++ b/packages/global-styles-ui/src/font-library/utils/index.ts
@@ -10,7 +10,6 @@ import type { DataRegistry } from '@wordpress/data';
  */
 import { FONT_WEIGHTS, FONT_STYLES } from './constants';
 import { fetchInstallFontFace } from '../api';
-import { formatFontFaceName } from './preview-styles';
 import type { FontFamilyToUpload, FontUploadResult } from '../types';
 import { unlock } from '../../lock-unlock';
 
@@ -114,14 +113,10 @@ export async function loadFontFaceInBrowser(
 		return;
 	}
 
-	const newFont = new window.FontFace(
-		formatFontFaceName( fontFace.fontFamily ),
-		dataSource,
-		{
-			style: fontFace.fontStyle,
-			weight: String( fontFace.fontWeight ),
-		}
-	);
+	const newFont = new window.FontFace( fontFace.fontFamily, dataSource, {
+		style: fontFace.fontStyle,
+		weight: String( fontFace.fontWeight ),
+	} );
 
 	const loadedFace = await newFont.load();
 
@@ -155,7 +150,7 @@ export function unloadFontFaceInBrowser(
 	const unloadFontFace = ( fonts: FontFaceSet ) => {
 		fonts.forEach( ( f ) => {
 			if (
-				f.family === formatFontFaceName( fontFace?.fontFamily ) &&
+				f.family === fontFace?.fontFamily &&
 				f.weight === fontFace?.fontWeight &&
 				f.style === fontFace?.fontStyle
 			) {
@@ -368,3 +363,37 @@ export function checkFontFaceInstalled(
 		} )
 	);
 }
+
+export function normalizeCSSFontFaceFontFamily( fontName: string ): string {
+	return `"${ fontName
+		.trim()
+
+		/*
+		 * CSS Unicode escaping for problematic characters.
+		 * https://www.w3.org/TR/css-syntax-3/#escaping
+		 *
+		 * These characters are not required by CSS but may be problematic in WordPress:
+		 *
+		 * - Normalize and replace newlines. https://www.w3.org/TR/css-syntax-3/#input-preprocessing
+		 * - "<", ">", and "&" are replaced to prevent issues with KSES and other sanitization that
+		 *   is confused by HTML-like text.
+		 *   is confused by HTML-like text.
+		 * - `,`, `"` and `'` are replaced to prevent issues where font families may be processed later.
+		 *
+		 * Note that the Unicode escape sequences are used rather than backslash-escaping so the
+		 * problematic characters are removed completely.
+		 */
+		// Escape existing backslashes before any other processing
+		.replaceAll( '\\', '\\5C ' )
+		// Carriage return + line feed must be the first newline replacement.
+		.replaceAll( '\r\n', '\\A ' )
+		.replaceAll( '\r', '\\A ' )
+		.replaceAll( '\f', '\\A ' )
+		.replaceAll( '\n', '\\A ' )
+		.replaceAll( ',', '\\2C ' )
+		.replaceAll( '"', '\\22 ' )
+		.replaceAll( "'", '\\27 ' )
+		.replaceAll( '<', '\\3C ' )
+		.replaceAll( '>', '\\3E ' )
+		.replaceAll( '&', '\\26 ' ) }"`;
+}
diff --git a/packages/global-styles-ui/src/font-library/utils/make-families-from-faces.ts b/packages/global-styles-ui/src/font-library/utils/make-families-from-faces.ts
index 5fd587c81692e7..6dfe0de3864683 100644
--- a/packages/global-styles-ui/src/font-library/utils/make-families-from-faces.ts
+++ b/packages/global-styles-ui/src/font-library/utils/make-families-from-faces.ts
@@ -2,33 +2,31 @@
  * WordPress dependencies
  */
 import { privateApis as componentsPrivateApis } from '@wordpress/components';
-import type { FontFamily, FontFace } from '@wordpress/core-data';
+import type { FontFamily } from '@wordpress/core-data';
 
 /**
  * Internal dependencies
  */
 import { unlock } from '../../lock-unlock';
+import type { FontFaceMetadata } from '../upload-fonts';
 
 const { kebabCase } = unlock( componentsPrivateApis );
 
 export default function makeFamiliesFromFaces(
-	fontFaces: FontFace[]
+	fontFaces: FontFaceMetadata[]
 ): FontFamily[] {
-	const fontFamiliesObject = fontFaces.reduce(
-		( acc: Record< string, FontFamily >, item: FontFace ) => {
-			if ( ! acc[ item.fontFamily ] ) {
-				acc[ item.fontFamily ] = {
-					name: item.fontFamily,
-					fontFamily: item.fontFamily,
-					slug: kebabCase( item.fontFamily.toLowerCase() ),
-					fontFace: [],
-				};
-			}
-			// @ts-expect-error
-			acc[ item.fontFamily ].fontFace.push( item );
-			return acc;
-		},
-		{}
-	);
+	const fontFamiliesObject = new Map< string, FontFamily >();
+	for ( const item of fontFaces ) {
+		if ( fontFamiliesObject.has( item.fontFamily ) ) {
+			fontFamiliesObject.get( item.fontFamily )!.fontFace!.push( item );
+		}
+
+		fontFamiliesObject.set( item.fontFamily, {
+			name: item.name,
+			fontFamily: item.fontFamily,
+			slug: kebabCase( item.fontFamily.toLowerCase() ),
+			fontFace: [],
+		} );
+	}
 	return Object.values( fontFamiliesObject ) as FontFamily[];
 }
diff --git a/packages/global-styles-ui/src/font-library/utils/preview-styles.ts b/packages/global-styles-ui/src/font-library/utils/preview-styles.ts
index 7661bc78899764..da5b69a1956158 100644
--- a/packages/global-styles-ui/src/font-library/utils/preview-styles.ts
+++ b/packages/global-styles-ui/src/font-library/utils/preview-styles.ts
@@ -82,44 +82,6 @@ export function formatFontFamily( input: string ) {
 	return formatItem( output );
 }
 
-/*
- * Format the font face name to use in the font-family property of a font face.
- *
- * The input can be a string with the font face name or a string with multiple font face names separated by commas.
- * It removes the leading and trailing quotes from the font face name.
- *
- * @param {string} input - The font face name.
- * @return {string} The formatted font face name.
- *
- * Example:
- * formatFontFaceName("Open Sans") => "Open Sans"
- * formatFontFaceName("'Open Sans', sans-serif") => "Open Sans"
- * formatFontFaceName(", 'Open Sans', 'Helvetica Neue', sans-serif") => "Open Sans"
- */
-export function formatFontFaceName( input: string ) {
-	if ( ! input ) {
-		return '';
-	}
-
-	let output = input.trim();
-	if ( output.includes( ',' ) ) {
-		output = (
-			output
-				.split( ',' )
-				// finds the first item that is not an empty string.
-				.find( ( item ) => item.trim() !== '' ) ?? ''
-		).trim();
-	}
-	// removes leading and trailing quotes.
-	output = output.replace( /^["']|["']$/g, '' );
-
-	// Firefox needs the font name to be wrapped in double quotes meanwhile other browsers don't.
-	if ( window.navigator.userAgent.toLowerCase().includes( 'firefox' ) ) {
-		output = `"${ output }"`;
-	}
-	return output;
-}
-
 export function getFamilyPreviewStyle(
 	family: FontFamily | FontFace
 ): CSSProperties {