The World T20 champion, who made his name hitting four successive sixes in the final over of the 2016 final against England, will join the squad before the opening group match at Surrey on July 6.
Brathwaite, 29, who has played three Tests, 28 one-day internationals and 25 T20s for West Indies, said: "I'm delighted to be joining Kent Spitfires for my first taste of county cricket.
"I have a good relationship with Sam Billings, having played in the same team at the IPL (Indian Premier League) and BBL (Big Bash League). Sam chatted to me about the opportunity to join and has told me a lot about the great support and atmosphere on T20 nights."
"Carlos is a proven match-winner," said Kent director of cricket Paul Downton. "He is an explosive ball striker and a skilful white-ball bowler with good variations and extensive experience in the 20-over format.
Australian all-rounder Marcus Stoinis will succeed Brathwaite as the squad's second overseas player ahead of a likely debut against Sussex on July 27.
Derbyshire have signed experienced Pakistan bowler Wahab Riaz, who will be available for the county's opening 10 T20 matches.
Big Bash LeagueCarlos BrathwaiteIndian Premier LeaguekentKent CountyWest IndiesWest Indies Cricket team
First Published: May 2, 2018, 6:58 PM IST