The 20-year-old, a free agent after he was released by the Seagulls at the end of last season, has agreed a one-year deal at his local club.
Reds boss Mark Yates told the club’s official website: “I think Shamir has got a lot of ability. He’s got raw pace and if anything he needs to be a bit more selfish because he gets into a lot of good goalscoring positions and is a real team player.
“I think he’s being quite brave in a way. A lot of clubs were interested in him but he’s a local lad and sometimes that brings its own pressure and extra expectation.
“He’s determined to show what he’s about to the Crawley supporters and I’m sure our fans will warm to him.”
Yates has also brought in Simon Walton, Joe McNerney and Luke Rooney this summer ahead of the new League Two season.