McCullum joins the Bears – Warwickshire’s T20 name – on a seven-match deal after playing a major role as New Zealand reached the World Cup final, where the Black Caps lost to co-hosts Australia.
The 33-year-old will link up with the Bears following New Zealand’s tour of England, with his first game scheduled to be against Lancashire Lightning at Old Trafford on Friday June 26.
“The Birmingham Bears had a great season last year, including winning the T20 Blast, and hopefully I can make a big contribution and ensure that we can progress in the tournament,” said McCullum.
“Edgbaston is a fantastic ground to play at and hopefully it will be rocking for the big Friday night matches. I???m really excited about becoming a Bear and the challenge ahead.”
McCullum is the leading run scorer in the history of T20 internationals, with 2,105 runs at an average of 35.67, including two centuries.
He has had spells with Sussex and Glamorgan, and was one of the leading run scorers in last year???s Indian Premier League – scoring 405 runs for the Chennai Super Kings.
Birmingham Bears director of cricket Dougie Brown??said: “Brendon???s dynamic performances in the World Cup have demonstrated once again exactly why he is one of the most feared batsmen in the game.
“Securing him for our last seven games has to make him one of the biggest overseas player signings in the competition???s history.
“His power at the top of the order and experience of playing in big matches are great assets to bolster our already-strong squad as we look to win through to the quarter-finals and defend our T20 Blast title.”