The 28-year-old, who has won five caps for Scotland, made 27 appearances as the Bluebirds won the Championship title last season.
"Craig is very experienced at this level and knows what it takes to be successful in the Championship," Garcia told Brighton's official website.
"He can play on either wing or up front as a second striker. He also has international experience and is a player who will improve our squad."
Brighton face Reading on Sunday.