City came into the game knowing Brighton were realistically the last team that they could catch in the battle to avoid relegation this season.
Both sides were also on a four-game losing streak, but while Cardiff were showing some fight to survive, Brighton were thrashed 5-0 in their most recent game on home soil against Bournemouth at the weekend.
And it was the Bluebirds who struck the decisive first blow just after the 20-minute mark thanks to a stunning effort from Nathaniel Mendez-Laing.
Brighton enjoyed more of the ball for the remainder of the half but were unable to find a way through a dogged Cardiff rearguard.
And Sean Morrison made sure of the win for the Welsh outfit with a header early in the second half as Neil Warnock’s men now sit just two points behind the 17th-placed Seagulls, who do have a game in hand.
Brighton boasted five changes from the Cherries’ drubbing as Pascal Gross, Solly March, Glenn Murray, Bruno and Alireza Jahanbakhsh replaced the suspended Anthony Knockaert, Martin Montoya, Yves Bissouma, Jurgen Locadia and Florin Andone.
Joe Ralls, Mendez-Laing and Oumar Niasse started for Cardiff in place of Harry Arter, Josh Murphy and Kenneth Zohore in three changes to the XI which lost 2-0 at Burnley.
Brighton were on the front-foot in a lively opening to the game and the hosts had a ninth-minute penalty appeal waved away after Lewis Dunk appeared to be pulled down by Bruno Manga in the area following a free-kick.
To make matters worse for the hosts, it was Cardiff who took the lead out of the blue in the 22nd minute when Junior Hoilett returned a pass to Mendez-Laing and he curled a wonderful strike into the top corner of Mat Ryan’s net from the edge of the area.
Brighton tried to respond, but they struggled to create any openings in the final third of the field.
Indeed, it was Cardiff who looked more of a threat on the counter-attack with Aron Gunnarson looping a header over the top before Dunk did well to deal with a dangerous cross from Ralls into the middle on 42 minutes.
The visitors did grab the second goal of the game just five minutes after the restart when Morrison got up in the area to head a Victor Camarasa cross past Ryan.
Cardiff continued to defend in numbers to prevent Brighton getting a foothold in the match with Manga doing well to head a dangerous Dunk ball back into the six-yard box, before Morrison prevented Andone from getting a clear shot at goal just after the hour mark.
Murray almost pulled one back on 70 minutes when Andone managed to squeeze a pass through to him just outside of the area, but the big striker lashed his subsequent effort over the crossbar.
The hosts continued to push men forward but the closest they came to getting a goal back came in stoppage time when Murry thumped the crossbar with a header.