Winless in their last six league fixtures and rapidly falling out of finals contention, first-half goals from Rafael Duran and Tomislav Uskok on Saturday afternoon gave the visitors the cushion they needed to see off Jake Girdwood-Reich's late consolation and escape with a win.
The three points moved Mile Sterjovski's side back up into sixth on 28 points, albeit with two more games played than seventh-placed Central Coast, who trail them by a point.
"We had a lot of conversations this week about attitude, accountability and staying together," Bulls skipper Luke Brattan told Sky Sport.
"And I think from the first minute we were together, and you can see it."
Conversely, defending premiers Auckland squandered the chance to vault Newcastle, who they beat last week, for top spot.
The Jets now have the chance to re-establish a four-point buffer on their rivals at the summit if they defeat Sydney FC on Sunday afternoon.
"Definitely, first half, there was no urgency to get back into that game," Auckland coach Steve Corica told Sky Sport.
"We didn't play well, we were second to everything, we just didn't win anything.
"Last week was probably our best performance against Newcastle; that was probably our worst."
Collecting a Brattan delivery before pivoting and whipping a deflected effort into the net, Duran's 11th-minute effort was the earliest goal Macarthur had scored this season and gave them a perfect start.
It should have been 2-0 six minutes later when Anthony Caceres picked out Chris Ikonomidis, but a finger-tip save from Michael Woud denied his glancing header.
Nothing, though, was stopping Uskok's header in the 44th minute, after the big centre-back stayed up after a free kick and rose to meet Ikonomidis' cross from the left.
The hosts created half-chances throughout the opening stanza, but Girdwood-Reich's header in the 49th minute was the first that required Alex Robinson to make a save, and the Bulls' Sime Grzan almost made it 3-0 in transition soon after.
Girdwood-Reich's 92nd-minute headed goal off a Francis De Vries corner cut the deficit, but the visitors' defensive discipline ensured the centre-back's attempts were the only shots on target the hosts managed all game.
