Jordan Richards' flying tackle on Jeff Hughes after just three minutes put the visitors on the back foot - earning the defender a straight red.
But the home side could not capitalise before the break. A Charlie Taylor shot, deflected off David Ball, was the closest they came to breaking the deadlock.
Steven Schumacher's shot was cleared off the line two minutes after the restart as Graham Alexander's men kept up the pressure.
Goalkeeper Scott Flinders was keeping Pools in it, superbly denying Jon Parkin as Fleetwood turned the screw.
And it was Parkin who eventually made the breakthrough, turning at the back post and slamming the ball into the far corner of the net.
The home side did not leave it long to bag a second goal. Sunderland's Mikael Mandron shrugged off the challenge of Jack Baldwin, charging forward and slipping a pass to Blackburn midfielder Marrow who scored with a neat finish to mark the start of his second spell at Highbury.
Andy Monkhouse tried to haul Hartlepool back into it, rattling the woodwork from 30 yards out.
But it was Fleetwood who should have added to their tally. Substitute Gareth Evans charged clear only to have his goal-bound effort deflected behind.