The home side piled on the first five goals of the game and outscored the Power nine scoring shots to two in the opening term.
But the visitors lifted their work-rate in the second quarter, outscoring Fremantle six goals to three to get back into the game.
Michael Barlow has continued his excellent form, collecting 16 possessions and kicking a goal.
Rhys Palmer has also been good with a game-high 18 disposals, a sign that the 2008 Rising Star winner is nearing peak form.
Fremantle 8.7 (55) leads Port Adelaide 7.3 (45)
