Brettle is set to take up his position on the committee after being appointed London head in December last year.
Brettle joins Turkish partner Asli Basgoz and New York partner Anthony Kahn on the committee, which works under firmwide chairman Hugh Verrier.
Brettle said: “My main responsibility will be to look after the people aspect of the firm. This means connecting the offices around the network.”
White & Case has come under fire in recent years for neglecting to represent London on its global management committee.
“My appointment is not viewed in that context,” said Brettle. “We’re all in one partnership. We need to view the firm in terms of separate offices.”