Cliftonville's Jay Donnelly pounced for a 73rd-minute winner at Portadown to make it three wins out of three for the 2013 and 2014 champions.
The skilful 20-year-old rounded sub keeper Billy Brennan to net after George McMullan had won possession and supplied the through ball.
Brennan had come on late in the first half to replace David Miskelly who sustained a knee injury.
Before the goal Cliftonville's James Knowles hit the bar with a free-kick.
The result sees Portadown drop their first points of the season, with Cliftonville and Linfield the only teams with maximum points after thee games.
Portadown made a bright start but Cliftonville held the upper hand after the interval.
Darren Murray, who withdrew his transfer request on Thursday, returned to the Portadown attack after missing the midweek win over Warrenpoint because of suspension.
He set up an early chance with a pull back from the bye-line but strike partner Gary Twigg was unable to apply a scoring touch in front of goal.
Before that Jay Donnelly, who looked impressive for Cliftonville, slid a low shot wide.
Just before the break Ports defender Chris Ramsey skied over from just a few yards out while Cliftonville winger Martin Donnelly's lob struck Brennan's crossbar.
In the second half Knowles saw his free-kick strike the crossbar.
But then came the decisive moment as Mark McAlister was dispossessed in his own half and McMullan slid the pass through for Donnelly to beat Brennan.
Late on Cliftonville's David McDaid was blocked out in a crowded penalty area.