The 30-year-old Hungary international is the third player to join the Tykes this week following the arrivals of Jonathan Greening and Emile Sinclair on loan from Nottingham Forest and Peterborough respectively.
Greening's Forest team-mate Marcus Tudgay arrived on loan in time to make his Barnsley debut in last weekend's draw at Bolton.
Buzsaky, who has 20 caps for Hungary, began his career with MTK Hungaria and arrived in England from Porto when he joined Plymouth in 2005.
He signed for QPR for £500,000 in January 2008 following an initial loan spell at Loftus Road and moved on to Portsmouth - where he has been a regular this season - in October last year.
Barnsley last week