John Salako's first half penalty decided the contest, however a host of missed chances cost the Bees the chance to win by a more comfortable margin.
The game sprung into life after 23 minutes when Salako's throughball following a fine run found striker Isaiah Rankin.
The former Bradford man was impeded by Vale defender George Pilkington and the referee made no hesitation in awarding the Bees a spot kick.
Worse followed for the Valiants as Pilkington saw red for a professional foul. Solako kept a cool head to stroke home left footed.
Brentford should have been more than just a goal to the good at the break. But poor finishing and a tremendous save from Vale custodian Mark Goodlad from a left foot shot from Deon Burton denied them. Goodlad limped off with an injury prior to half time, replaced by Jonathan Brain.
Moments into the second half Kevin O'Connor playing at right back in the absence of Scott Fitzgerald saw his right foot shot cannon off the cross bar as Martin Allen's men signalled their intent. The Bees introduced Jamaican international Jamie Lawrence for his debut, however further chances to extend their lead were wasted as Brain and Vale stood firm.
The 10 men could not find a way to penetrate Brentford's rearguard, non the less despite adding an extra forward mid way through the second half. The Bees nervously held on for a valuable three points.