The Seagulls fast start proved enough to give them their first Championship win since August 23, leaving fellow-strugglers Wigan with just one victory in their last 11 games.
Brighton boss Hyypia called up winger Elliott Bennett, on loan from Championship rivals Norwich, and he immediately made his presence felt as Albion dramatically took the lead after just 54 seconds.
Bennett released Sam Baldock down the right and his accurate low cross was driven in from 12 yards by midfielder Gardner for his first goal since joining on loan from Aston Villa.
Brighton had gone behind in 10 of their previous 15 league games and this was just the start that Hyypia would have been praying for.
Former Newcastle winger Kazenga LuaLua caused plenty of problems early on and his good play set up Joao Teixeira in front of goal, but his powerful shot came back off the crossbar.
Wigan threatened for the first time midway through the half when midfielder Roger Espinoza crossed and striker Martyn Waghorn put a glancing header wide of keeper Christian Walton’s left-hand post.
England Under-20 stopper Walton, 18, was making his home debut, with the Seagulls unable to play Ali Al-Habsi against his parent club.
Waghorn was off target again with a shot on the turn which flew over after a cross by Irishman James McClean.
Wigan keeper Scott Carson made a straightforward save to take a header from Elliott Bennett before opposite number Walton held a 20-yard free-kick by defender James Tavernier.
LuaLua found himself in space on the edge of the area shortly after the interval and his low shot was taken by the alert Carson.
Walton came to Brighton’s rescue by saving a low shot from Waghorn before parrying a goal-bound drive by Adam Forshaw.
Waghorn threatened again by getting in between Albion’s two centre-halves but his left-foot shot was well saved by the diving Walton.
Wigan made their first change when James McClean gave way to Callum McManaman while Brighton boss Hyypia sent on Rohan Ince in place of Teixeira.
Utility player Greg Halford, signed on loan from Nottingham Forest, came on for his Seagulls debut in the closing stages with Bennet forced off after taking a blow to the calf.
Wigan improved after the break but Brighton held on quite comfortably to record a much-needed victory.