Lewis, who was already freelancing for Lucky Generals, has been hired as the agency’s first head of design and will report to Danny Brooke-Taylor, its co-founder and creative chief.
Lewis began his career as a junior designer on the now defunct clubbing magazine Sleazenation before joining Abbott Mead Vickers BBDO in 2003.
He moved to Fallon in 2004 and spent a year in South Africa at Am I Collective in 2007. In 2012 he opened his own consultancy.
Lewis said: "I love the way Lucky Generals see design strategically, not just as a bolt-on. There's a real momentum about the place and I'm delighted to join."
Brooke-Taylor said: "Pete has already made a huge difference on briefs for the likes of Amazon and Twitter. It's great to have him on board as a permanent hire."