Use Different Single Templates For Different Categories

You want to use a different single template file for only one category in WordPress. First, create the special single template file. Name it whatever you want. Next, open your theme’s single.php. At the very top of single.php, before the head, insert this:

<?php if ( in_category('the-special-cat-slug') ) 
{
include 'special-singlefile.php';} 
else { ?>

In the code above, you must make change ‘the-special-cat-slug’ in line 1 to your own category slug (the one getting the special template file). Also, change ‘special-singlefile.php’ in line 3 to the name of your special single template file.

Next, at the very end of single.php, even after the closing html tag, insert this:

<?php } ?>

Variation

This example uses 2 special single template files for 2 categories. Then it calls a 3rd single template file for posts in a 3rd category, but for posts who are also not in some other category (‘cat-slug-4’). Then it calls a 4th single template file for posts that are tagged with tag id #56.

<?php if ( in_category('cat-slug-1') ) 
{ include 'special-singlefile1.php';}
elseif ( in_category('cat-slug-2')) 
{ include 'special-singlefile2.php';}
elseif ( in_category('cat-slug-3') && !in_category('cat-slug-4'))
{ include 'special-singlefile3.php';}
elseif (has_tag('56')) { 
include 'special-singlefile4.php';
} else { ?>

Don’t forget the closing curly brace at the very bottom of single.php:

<?php } ?>