On 16 July 2015, Younes signed a three-year contract for Dutch club Ajax, until 30 June 2018, with an option for an additional year for €2,5 million. After an injury, which kept him out for the start of the championship, he made his debut as a starter against Groningen (2–0) on 26 September. The following week he scored his first goal for Ajax, against PSV in a 1–2 defeat. Over the weeks, the player found continuity and concluded his first season with eight goals and nine assists in 35 total games. On 20 October 2016, he scored his first goal in a UEFA competition by scoring against Celta Vigo (2–2) in the UEFA Europa League. At the end of the season he played in the 2017 UEFA Europa League final lost to Manchester United. Younes was the player with the most dribbles in the competition.