After a largely frustrating afternoon, Ollie Watkins broke the deadlock with a fine curling right foot finish.
Captain Tyrone Mings then sealed the points when he side-footed home after a spell of intense pressure from the hosts.
The victory snapped Villa’s five-match losing streak and saw them climb one place to 15th in the Premier League table.
Gerrard, in his first match since replacing Dean Smith, celebrated both goals wildly in the technical area and left the field at full-time punching the air.
For much of the day this threatened to be an anti-climax as Villa huffed and puffed against a disciplined and well-organised Brighton. The hosts managed just two efforts on target in the first 83 minutes.
Yet the finish was impressive. Anwar El Ghazi, introduced off the bench seconds earlier, helped drag away two defenders and Watkins took advantage of the space to fire home his third goal of the season.
After that Villa bombarded the visitors, Mings grabbing the second after the Seagulls defence failed to clear. Villa’s winning margin would have been even wider had goalkeeper Jason Steele not saved acrobatically from Leon Bailey in stoppage time.
Though there can be no ignoring how unconvincing Villa were for much of the afternoon, the result was hugely important, creating much-needed breathing room over the bottom three.
Villa’s team featured three changes from the team which lost at Southampton in Smith’s final match in charge.
Fit-again Danny Ings returned, while Jacob Ramsey was given the nod in midfield and Emi Buendia pushed into a more attacking role on the right.
Anwar El Ghazi and Leon Bailey dropped to the bench, along with Axel Tuanzebe as Ezri Konsa back in defence following his suspension. Konsa’s return meant the back four which enjoyed so much success last season started together for the first time since the opening day defeat at Watford.
A huge roar greeted Gerrard when he emerged from the tunnel but the noise inside Villa Park at kick-off quickly quietened as his team struggled to make headway.
Villa created just one big chance in the first-half. McGinn, who looked the likeliest to unlock the visiting defence, released Watkins with a fine ball over the top. From there it was played back to Targett who delivered a first time cross which Cash, arriving at the far post, headed a little too close to Steele, who saved low.
Otherwise the hosts looked short on ideas with Brighton, comfortable and dominating possession, looking the more dangerous team as half-time approached.
Twice Emi Martinez was called on to keep Villa level, first beating away Leandro Trossard’s powerful drive at the near post. Then, just seconds before the break, the goalkeeper was quickly off his line to deny Tariq Lamptey after Jakub Moder’s cross had found its way to the right-back.
Villa needed a spark and almost found it early in the second half. McGinn whipped in a free-kick and when Mings headed back across goal, Steele palmed the ball away from Ings at full stretch.
But the hosts again failed to build on their early momentum and it was Brighton, again, who looked the more composed unit. When Cash went down under the lightest of pressure from substitute Solly March, it summed up Villa’s increasing desperation.
Gerrard changed two-thirds of the forward line as Leon Bailey and Ashley Young replaced Ings and Buendia but still Villa toiled, their lack of certainty in attack summed up when McGinn conceded a goal kick trying to beat his man, having turned down the option to cross or shoot.
The breakthrough came from nowhere. Nakamba cut out a dangerous cross on his own six-yard line and found Young, who motored toward the halfway line before finding Watkins in space on the wing. The striker cut inside and took advantage of being allowed to run along the edge of the box before curling a right-footed finish into the far corner.
Villa Park erupted, as did Gerrard in his technical area. With renewed vigour the hosts poured forward and within five minutes had their second. McGinn crossed and Webster could only clear as far as Mings, who lifted a right-footed finish into the net.
84 GOAL Ollie Watkins breaks the deadlock, curling a right-footed shot into the far corner.
89 GOAL Tyrone Mings doubles Villa’s advantage, side-footing home with his right foot after an intense spell of home pressure.
Villa (4-3-3): Martinez, Cash, Konsa, Mings, Targett, McGinn, Nakamba, Ramsey (El Ghazi 84), Buendia (Young 74), Ings (Bailey 66), Watkins Subs not used: Tuanzebe, Hause, Sanson, Chukwuemeka, Davis, Steer (gk).
Brighton (4-2-3-1): Steele, Webster, Dunk, Duffy, Lamptey (Maupay 79), Gross (MacAllister 89), Bissouma, Lallana, Cucurella (March 64), Moder, Trossard Subs not used: MacAllisteLocadia, Richards, Burn, Veltman, Sarmiento, Scherpen (gk).