Lukaku headed Chelsea into a 1-0 lead on 27 minutes, turning in a corner in style.
The Belgium hitman shrugged off Neal Maupay’s measly challenge, with the Brighton’s striker’s protests dismissed without issue by the officials.
Chelsea’s lead eased their latest injury frustration, with Reece James hobbling off with a suspected knee problem.
Albion had decent spells as Adam Lallana and Alexis Mac Allister both forced Mendy into action while Tariq Lamptey was a lively presence on the right.
Danny Welbeck headed Brighton level at 1-1 in added time. The former Arsenal striker nodded home to sting Chelsea, with the angry home fans throwing a blue smoke bomb onto the pitch.
Here's how the Albion players rated.
9. Moder 6
Played in all but one of Brighton's PL games this season. Went close at the start of the second half with an improvised effort.
10. Mac Allister 7
Played with energy and skill and always looking to strike on goal. Liked his performance.
11. Maupay 7
Often isolated in the early stages but worked hard for the team. Elbowed in the face by Lukaku in the build up to the first goal. Flashed an effort just wide on 56 minutes. Huge amount of work
12. Mwepu 6
On for Lamptey on 66. Added energy but a bit loose in possession at times