The former Leeds striker broke the deadlock in the 46th minute before Steven Gerrard went down in the box under a Chris Morgan challenge, gifting Robbie Fowler the chance to get off the mark from the penalty spot.
United boss Neil Warnock, serving a one-match ban in the stands, dished out last season, was delighted with his side, but believes they should have had all three points.
The Sheffield side started brightly and Danny Webber was inches from connecting with a quickly taken David Unsworth free-kick as United caught Liverpool napping.
Jamie Carragher almost opened the door for new signing Hulse as he failed to cut out a pass down the right flank, but the England defender showed his experience by recovering quickly to nick the ball away from the feet of the big striker.
Liverpool, who picked up the Community Shield from arch rivals Chelsea last Sunday, then showed their class. Jan Kromkamp slid the ball to Craig Bellamy, who twisted past his marker and unleashed a low angled drive from 15 yards which beat Paddy Kenny but flashed the wrong side of the far post.
United were sliced open on 23 minutes, when John Arne Riise charged down the left flank with Paul Ifill chasing. The Reds left-back beat the advancing Kenny to fire over a fierce cross, which was headed away by Morgan.
The Norway international fell badly under Ifill's challenge and was stretchered off with a serious ankle injury to be replaced by Mark Gonzalez.
United were in trouble again minutes later from Gerrard's curling free-kick. Armstrong almost put the ball into his own net as he stuck out a foot, but Kenny reacted quickly to palm the ball round the post for a corner.
There was a further injury problem for Liverpool in the 35th minute, when Carragher was forced to limp off following a challenge from Hulse. Daniel Agger was the replacement.
The Anfield side almost snatched the lead three minutes later when Fabio Aurelio's curling free-kick forced Kenny in to an eye-catching save.
Hulse had the ball in the net three minutes before the interval after Webber's darting run, but it was ruled out by referee Rob Styles for offside.
United swept ahead 56 seconds after the re-start after winning a free-kick 22 yards out. David Unsworth curled the ball over and the unmarked Hulse darted forward to steer his header past Jose Reina from six yards.
Liverpool were almost back on level terms two minutes later, but Sami Hyypia's header from Gerrard's corner cannoned to safety off the post.
The visitors drew level on 70 minutes with a hotly-contested penalty after Gerrard linked cleverly with Robbie Fowler and then tumbled over after half-tripping over Morgan's outstretched leg.
Fowler scored the coolest of spot-kicks after sending Kenny the wrong way.