Defender Eric Deloumeaux pounced for a vital equaliser as Livingston came from behind to share the points in a scintillating relegation battle.
Stevie Crawford opened the scoring for United
Derek Lilley had cleared off the line early on to deny Dundee United defender Gary Kenneth.
But United took a deserved lead through a diving header by Stevie Crawford following a Mark Kerr cross.
Livi came battling back after the break and Deloumeaux fired home following a goalmouth scramble.
Third bottom United had gone into the game seeking third win in a row, while bottom of the table Livi were buoyed by the surprise 3-0 win away to Hibernian last weekend.
United caretaker-manager Gordon Chisholm recalled Scotland international Crawford in place of Jason Scotland.
Hassan Kachloul came within inches of opening the scoring for unchanged Livi with a fine 20-yard effort, but the shot slipped wide of Tony Bullock's left-hand post.
Gary Kenneth thought he had opened his account United with a magnificent header from Mark Wilson's cross, but Lilley made a crucial late block on the line.
Livi were unable to keep the ball out of the net in the 37th minute, when Crawford dived to head a Kerr cross beyond Roddy McKenzie and into the bottom right corner of the net.
Stuart Duff was through one-on-one with McKenzie and should have added a second but sent a shot straight into the goalkeeper's arms.
United had a very strong penalty claim waved away within 20 seconds of the restart.
McIntyre broke into the box and whipped the ball through Emmanuel Dorado's legs and fell to the turf.
Livi should have equalised less than a minute later, but Lilley missed the ball with an almighty swing a yard from the line.
The goal eventually came when Bullock raced out to gather Kachloul's cross but was beaten to it by Lilley.
The striker missed the ball with the goal at his mercy, but Deloumeaux took charge and booted home.
Barry Robson went close to winning the game for United and an interception by David McNamee prevented Collin Samuel finding fellow substitute Jason Scotland in front of goal.
Dundee Utd: Bullock, Kenneth, Ritchie, Archibald, Wilson, Kerr, Brebner, Duff (Samuel 67), Robson, Crawford (Scotland 77), McIntyre.
Subs Not Used: Colgan, Dodds, Grady, Gardiner, Cameron.
Goal: Crawford 37.
Livingston: McKenzie, McNamee, Deloumeaux, Dorado (Rubio 81), Bahoken, Kachloul, Dair, O'Brien, Vincze, Lilley, McMenamin.
Subs Not Used: Meldrum, Easton, Brittain, McPake, Horvath, Snodgrass.
Goal: Deloumeaux 61.
Ref: K Toner