[5] Signing a four-year contract, binding him to the club until the Summer of 2013, he initially joined the youth ranks where his first season with Ajax was stalled by injuries.

He made his professional debut on 3 April 2011, as he played the second half of Ajax' 3–0 victory against Heracles Almelo being substituted on for Daley Blind.

However, in the match against rivals PSV in September 2011, Boilesen suffered a hamstring injury which would see him sidelined until February 2012, following a sprint duel with Jeremain Lens.

[7] On 27 July 2013, Boilesen made his return to the first team in the 2013 Johan Cruijff Schaal match against AZ, coming on for Daley Blind in the 106th minute of the 3–2 win (a.e.t.).

On 18 September 2013, Frank de Boer surprisingly put Boilesen on the left wing in the UEFA Champions League match against FC Barcelona at Camp Nou.

Helping Ajax to a 2–1 win over FC Barcelona on the return leg of the series at the Amsterdam Arena, Boilesen was selected for the UEFA Champions League Team of the Week for matchday 5.