McNab, who has been a partner at Travers since 2007, has a particular expertise in renewable and conventional energy, climate change and clean technologies.
McNab also founded the Leapfrog charity, which undertakes pro bono work supporting climate change projects and low carbon innovators by providing legal, fundraising and project finance advice.
The project launched in September 2009 after three years’ work and earned McNab a place in The Lawyer’s Hot 100 list.
McNab said of his new role: ‘‘Simmons & Simmons has great relationships with corporates in the energy, pharma, waste and manufacturing sectors, and a range of leading investor and governmental clients.
“I’m looking forward to working with lawyers across practices and internationally to further develop their environment practice.’’