Bertrand scored his first professional goal for Chelsea in the Community Shield match against Manchester City on 12 August 2012, which they went on to lose 3–2. He started in the first league match of the season against Wigan Athletic playing as a winger. On 5 September 2012, Bertrand signed a new improved five-year contract with Chelsea. On 25 September, he scored his second professional goal in a League Cup match against Wolverhampton Wanderers at Stamford Bridge, which Chelsea won 6–0.