The 21-year-old Brazilian scored in either half to take his tally to six for the season.
Lewis Dunk equalised for Brighton after Everton had taken the lead, but this defeat means the Seagulls' three-game winning run has come to an end.
Seamus Coleman put Everton back ahead at the start of the second half with his first goal for 22 months.
The Everton captain fired a low shot past Mat Ryan to put Everton ahead.
Richarlison's brace means the 21-year-old now has more goals this season that he managed in the entirety of last campaign.
The result leaves Everton in 10th place, while Brighton are in 12th.