Middlesbrough looked to have victory secure as goals from Marvin Emnes, Barry Robson and Leroy Lita put them 3-1 up after 53 minutes.
But the home defence crumbled as npower Championship promotion-chasing Swansea piled forward in a pulsating finish, allowing Scott Sinclair, Ashley Williams and Craig Beattie to add to Nathan Dyer's earlier goal.
"There was some very poor defending out there," said disappointed Mowbray. "You should never lose grip of a two-goal lead like that but it was all self-inflicted. We have shot ourselves in the foot.
"It comes down to some very poor decision-making on our part."
Source: PA
Source: PA