The home side set the tone early with a Marlee Francois free kick almost bouncing in untouched, evading everyone in the box before just going by the far post.
Against the run of play, Sydney FC defender Rhyan Grant fired a shot over the bar a few minutes later.
Auckland FC opened the scoring around the 20-minute mark after Francis de Vries sent in a very high wide cross into the box, which Hiroki Sakai headed back across goal. Louis Verstraete first missed but Cosgrove got on to his left foot for his seventh of the season and joined the top of the golden boot standings.
It appeared Auckland’s second wasn’t far away – the chances kept coming, but they continued to be chalked up as missed opportunities.
A Verstraete header was saved over the crossbar by Harrison Devenish-Meares, at the other end Woud then denied Víctor Campuzano, proving to be up to his first task of the day.
Cosgrove then missed a chance on goal when Sydney goalie Devenish-Meares misjudged a long throw but the attempt from the Auckland FC striker somehow went wide from close range.
Auckland FC suffered a blow just before halftime when Lachlan Brook left the field with a back injury, though Steve Corica had the luxury of replacing his standout player this season with last year’s best, Guillermo May.
May missed a chance from in front of goal as Auckland FC continued their run of missed opportunities to start the second half. Then, in a thrilling stretch of play, first Sydney FC’s Tiago Quintal hit the post, only for Auckland to counter, before Cosgrove passed to an open May, who then also hit the post.
Shortly afterwards, Cosgrove was denied again by a brilliant save when Devenish-Meares somehow got a hand to block a header from close range.
The near-chances kept coming for Auckland FC.
May had another opportunity in the 80th minute, again set up on the break by Cosgrove, but on his less favoured right foot he couldn’t beat the keeper. Five minutes later he hit the post again, before Jesse Randall fired a shot wide from a breakaway.
In the end Auckland FC finished with 25 shots, eight on target. But more importantly they denied every one of Sydney FC’s 16 attempts – holding on in the closing minutes where they have failed in recent weeks.
“We probably could have made it a little bit easier for ourselves,” de Vries told Sky Sport after the win. “They could have scored too but we definitely could have had two or three more. Try and make those posts a little more smaller and we might have a few.
“We’ve spoken a lot this week about holding the belief in the last 15 minutes because we’ve been conceding late goals. I thought the communication was much better everyone and everyone was working their socks off. It was nice to get through that one,” de Vries added.