On 15 June 2016, Lewis signed for Aberdeen. He made his debut for the club on 30 June 2016, in a Europa League First qualifying round tie against Fola Esch. Lewis started all matches for the Dons in 2016–17, and signed a new deal at the end of the season to keep him at the club until 2020.
Lewis made his debut for the England under-21s on 15 May 2008, in a friendly against Wales. He replaced Joe Hart at half time and carried through a clean sheet, in a game that saw England win 2–0.
In May 2008, he received a call-up to the senior England squad, replacing an injured Chris Kirkland for the friendlies against USA and Trinidad and Tobago. However, Lewis was an unused substitute for both games.
On 18 August 2008 he started and played for the under-21 England side at Hull City’s KC Stadium.
He made his third appearance for the under-21s in a friendly against the Czech Republic only to come off with an ankle injury after 33 minutes. He came on from the bench on the game against Azerbaijan coming on for Lee Cattermole as an outfield player.