The 19-year-old Northern Ireland youth international could go straight into boss Danny Wilson's squad for Saturday's league game at Charlton.
The right-back, who signed a new contract at Anfield last year, will stay at Oakwell until after the home league game against Ipswich on February 8.
"It's great to be here and there are some good games coming up, which I'm looking forward to being involved in," McLaughlin told Barnsley's official website.
"I like to get forward, it's a good part of my game, but obviously if you're a right-back your first job is defending and to be solid in defence.
"I've been training with some fantastic players at Liverpool and that can only bring you on and improve you as a player, which I now want to be able to take into here and to play some great football at Barnsley.
"While I'm here I want to be playing as much football as I can and do well for the team.
"Hopefully I'll be able to provide more attacking options going forward and chip in with a few assists and goals and help bring us up the table."
McLaughlin made an unofficial first-team debut for Liverpool in a pre-season tour game against AS Roma in 2012, but is otherwise awaiting his first appearance.