Dean was born in Middlesbrough. He grew up with his mum, and says his favourite song from Aladdin is Proud of Your Boy as he wants to make his mother proud. John-Wilson used to pick his younger sister up from dance class and decided to have a go himself. He studied tap, jazz, and gymnastics and did a BTEC in performing arts. Afterwards, he went to London's Mountview Academy of Theatre Arts.
John-Wilson toured the UK with Sister Act and starred as Aquino in Here Lies Love at the National Theatre. He also has appeared in From Here To Eternity in the West End at the Shaftesbury Theatre. He starred in the title role in the original West End production of Disney's Aladdin at the Prince Edward Theatre. In 2016 John-Wilson starred in Miss Atomic Bomb opposite Catherine Tate at the St. James Theatre.
In mid-2018, he played the role of Lun Tha in the West End revival of The King and I. In February 2020, he appeared in the ninth series of The Voice UK, and in March 2020, he portrayed the role of Mark Casey in an episode of the BBC soap opera Doctors.
