May joined Scottish Premiership club Aberdeen on a four-year deal in August 2017, for an undisclosed fee thought to be around £300,000, reuniting with former St Johnstone manager Derek McInnes. Although initially given the squad number of 18, May later changed to 83, in honour of Aberdeen winning the UEFA Cup Winner’s Cup in May 1983. May scored his first goal for Aberdeen in a 2–1 victory over Dundee; coincidentally this was timed at the 11th minute of the game, creating a further reference to the club’s European honours (11 May 83).
On 5 August 2013, May was called up for the Scotland U21 team. On 30 September 2014, May was called up to the senior Scotland national football team for Euro 2016 Group D qualifying matches against Georgia and Poland.
On 18 November 2014 he made his international debut for Scotland, coming on as a substitute in the 67th minute in a friendly against England at Celtic Park.