Phil Foden fired the English champions in front, but Brighton were well worthy of the point given to them by Julio Enciso’s stunning long-range strike.
Brighton, who had already secured European football next season for the first time in the club’s history, are now certain to finish sixth.
City did at least stretch their unbeaten run in all competitions to 25 games as Pep Guardiola’s men opened up an eight-point lead at the top of the table with one game remaining.
Guardiola heaped praise on Brighton boss Roberto De Zerbi pre-match, hailing the Italian as one of the most influential managers of the last 20 years.
The City coach showed his respect by restoring a number of star names to his side that missed Sunday’s 1-0 win over Chelsea to toast a fourth league title in five years.
Erling Haaland returned among six changes and could have had a seventh hat-trick of the season inside half an hour.
The towering Norwegian headed over Foden’s inviting cross on five minutes.
Haaland then had a poor touch to blame for not beating Jason Steele when clean through on goal.
At the third time of asking he took no chances as Haaland unselfishly squared with just Steele to beat for Foden to convert his 15th goal of the season.
But after a slow start, Brighton soon began to live up to Guardiola’s billing as the champions were rocked back on their heels.
Danny Welbeck’s free-kick came crashing off the bar and Facundo Buonanotte should have done better with his finish after sauntering through the City defence.
Kaoru Mitoma also saw an equaliser ruled out for handball.
But there was no stopping Enciso’s leveller when it did come as the Paraguayan picked up Levi Colwill’s pass and smashed an effort into the top corner for his first goal at the Amex.
Brighton had the ball in the net for a third time in the first 45 minutes moments later only for Welbeck to be flagged offside from Mitoma’s pass.
The second period was less filled with goalmouth action despite the electric pace of the game.
Haaland thought he finally had his 53rd goal of the season when he headed home Cole Palmer’s cross 15 minutes from time.
But a VAR review caught out City’s prolific number nine as he had pulled Colwill’s shirt to create the space for a free header.
Tempers briefly flared on the touchline after that decision with Guardiola shown a yellow card by the referee.
There were also minor injury concerns for City ahead of the FA Cup and Champions League finals next month as John Stones and Bernardo Silva were not moving freely as they were replaced in the closing stages.
But it was all smiles at the end as Guardiola and De Zerbi shared a warm embrace of mutual admiration after the full-time whistle.