The blues squeezed past Swansea on Saturday after coming back from 2-0 to win the match 3-2 and the Seagulls almost emulated City with a comeback of their own.
Traing 2-0, Brighton pulled it back to 2-2 and went through by winning the ensuing penalty shoot out after extra time led to no further goals.
The match will be Brighton's first Semi-Final since 1983, when they lost to Manchester United. Ominously for City, the Seagulls beat City 4-0 on their way to the final that year and the blues will be eager to avoid a repeat of that particular scoreline.
The match will be played on the weekend of 6th and 7th April.