McClay is currently global co-head of marketing and business development at Freshfields Bruckhaus Deringer, and will move to his new role in the new year.
Baker & McKenzie is consistently ranked among the top three largest law firms in the world by various publications' rankings. The firm has recently promoted Julia Hayhoe to the position of global director of strategy implementation, having previously been in the role McClay is due to fill.
McClay "will be focused on further developing the firm's brand and institutionalising client relationships, operating as part of the wider global marketing and business development function", according to a press release from Baker & McKenzie.
McClay will also have responsibilities with the firm's South African operations and sit on its eight-member London management committee.
He joined Freshfields in 2011, and before that worked for Barclaycard in a variety of commercial and customer-facing roles in a 20-year stint.