diff --git a/packages/base-styles/_mixins.scss b/packages/base-styles/_mixins.scss
index 9f089b8d9e8322..e61541f0270570 100644
--- a/packages/base-styles/_mixins.scss
+++ b/packages/base-styles/_mixins.scss
@@ -284,7 +284,6 @@
 	}
 
 	&::-moz-placeholder {
-		opacity: 1; // Necessary because Firefox reduces this from 1.
 		color: $dark-gray-placeholder;
 	}
 
diff --git a/packages/components/src/textarea-control/styles/textarea-control-styles.ts b/packages/components/src/textarea-control/styles/textarea-control-styles.ts
index 022ce3560ea3a5..84dd2da0e53c03 100644
--- a/packages/components/src/textarea-control/styles/textarea-control-styles.ts
+++ b/packages/components/src/textarea-control/styles/textarea-control-styles.ts
@@ -62,7 +62,6 @@ export const StyledTextarea = styled.textarea`
 	}
 
 	&::-moz-placeholder {
-		opacity: 1; // Necessary because Firefox reduces this from 1.
 		color: ${ COLORS.ui.darkGrayPlaceholder };
 	}
 
@@ -76,7 +75,6 @@ export const StyledTextarea = styled.textarea`
 		}
 
 		&::-moz-placeholder {
-			opacity: 1; // Necessary because Firefox reduces this from 1.
 			color: ${ COLORS.ui.lightGrayPlaceholder };
 		}
 
diff --git a/packages/editor/src/components/post-text-editor/style.scss b/packages/editor/src/components/post-text-editor/style.scss
index 5391588d906d8d..ad7b3383db2aa5 100644
--- a/packages/editor/src/components/post-text-editor/style.scss
+++ b/packages/editor/src/components/post-text-editor/style.scss
@@ -41,8 +41,6 @@ textarea.editor-post-text-editor {
 
 	&::-moz-placeholder {
 		color: $dark-gray-placeholder;
-		// Override Firefox default.
-		opacity: 1;
 	}
 
 	&:-ms-input-placeholder {