The sides were locked 0-0 at halftime but the Gulls pulled away to a 2-0 win thanks to second-half goals to Alex Morgan (58) and Sean Canham (89) at Percy Doyle Reserve.
Coach Jamie Harnwell believed it was a deserved win.
“I thought we controlled the whole game, although I would have liked us to create a few more chances, but I thought we were solid the whole time,” he told nplwa.com.au.
ECU threatened to score early in both halves, its best chance coming six minutes after the break when the dangerous Tommy Amphlett found himself one on one with Gulls keeper James Morgan, who made an important save. Sorrento scored minutes later and controlled the match from then on.
The Jacks face Armadale at home on Saturday, while Sorrento faces Floreat Athena away.