Ten-man Bulli survived a second half fightback from Port Kembla to secure a hard-earned 2-1 win at Balls Paddock on Saturday.
Two first half goals proved enough for the Northern Suburbs club to grab the points despite a tense second stanza after centre-back Stuart Lowrie was dismissed midway through the half.
It came close to an hour after Cameron Littler had opened the scoring with a classy finish following some strong lead-up work by Hayden Mowbray.
Mowbray then turned provider again in the 42nd minute when his through ball found Ben McDonald to double the hosts' advantage at the break.
Port came out of the blocks firing in the second half and pulled a goal back through Peter Richardson after a goalmouth scramble in the 56th minute.
Their chances of a fightback soon improved when Lowrie was handed his marching orders.
But try as they may, the champions couldn't pierce Bulli's defence which was already without regular centre back Corey Horner.
"We scored two good goals but besides that it was a pretty tough afternoon," Bulli coach Ben Smith said afterward.
"Credit to Port Kembla. They are obviously trying to climb the ladder and were up for the game. I don't think we were at our best on the afternoon and then we had a player sent off which compounded.
"Certainly in the second half they had the territorial advantage and we had to scramble a few times to keep them out."
Against the odds in the second half, Smith lauded his squad's resilience at the back to secure their second win this season over their 2013 grand final rivals.
"It wasn't our best performance but we were very impressed with our effort and determination in that last 20 minutes when we were down a man," Smith said. "Not a lot of things were going for us at the time so the boys dug deep and got the important three points that we needed."
The win was Bulli's seventh straight triumph and helps them remain top of the competition, one point clear of Dapto Dandaloo Fury.
In other matches, Wollongong United chalked up their fourth win in succession with a 4-2 victory over Wollongong Olympic. Albion Park White Eagles smashed Cringila Lions 6-0 and Tarrawanna gave Woonona a 4-0 drubbing. Fernhill and Bellambi drew 4-4.