A double from Barnsley substitute Andy Gray prevented Cardiff moving into the automatic promotion places in the npower Championship as the visitors secured a share of the spoils in a 2-2 draw.
A stunning Peter Whittingham strike had given the hosts a 21st-minute lead, but Gray coolly fired home just eight minutes later to level.
Dekel Keinan's first goal for Cardiff looked to have won it with eight minutes to play, but Gray's near-post header with two minutes remaining dented Cardiff's hopes of a top-two finish.
Craig Bellamy and Jay Bothroyd wasted chances after the break, with the former also furious not to be given a first-half penalty after going down under a challenge from Jason Shackell and Cardiff boss Dave Jones will reflect on a missed opportunity following Swansea's defeat at Derby on Saturday as his side remain fourth in the table.
Despite consecutive defeats to Ipswich and Crystal Palace, Jones opted to stick with the same side which lost at Selhurst Park, although Seyi Olofinjana returned on the bench.
Barnsley boss Mark Robins made one change with defender Matt Hill replacing Jim O'Brien, while the Tykes were dealt an early blow when Danny Haynes was forced off in the 11th minute with what appeared to be an ankle injury.