Poyet was sacked by the club on Sunday following an internal investigation after the Uruguayan was suspended in the aftermath of the club's play-off semi-final defeat.
Garcia will now take charge of the club and says is he looking forward to working with the Championship side.
|WHAT NEXT FOR POYET?
|9/2||Brighton are 9/2 with Coral to win promotion to the Premier League next season
Brighton chairman Tony Bloom also welcomed the new head coach to the club adding: "We are delighted to have Oscar here to help us prepare for the new season and plan what promises to be another exciting campaign for the club."
Garcia featured for Barcelona, Valencia and Espanyol during his playing career and spent a year in charge of Maccabi Tel Aviv, winning the title before resigning from his post.