Adeliyi was born in Brampton, Ontario but frequently visited Brooklyn, New York to pursue acting. She graduated from the American Academy of Dramatic Arts, performing in local theater, before returning to Toronto in 2008.

One of her earliest film roles was an uncredited bit part in the film John Q; on set, she met Denzel Washington, who she claims "inspired" her to continue pursuing acting. In 2009 she starred as the lead in the African Theatre Ensemble production of Efua Sutherland's The Marriage of Anansewa. Also that year, she starred in the Canadian TV series Flashpoint. She was nominated for Best Performance by a Female – Film at the 2012 Canadian Comedy Awards for her performance in French Immersion.

In 2014, Adeliyi was dubbed "Shakespeare’s First Jamaican-Nigerian Lady MacBeth" when she played the role at the Sterling Theatre in Toronto.

In 2017, Adeliyi attracted media attention in Canada after an incident at Toronto's Kingsway Theatre. The establishment does not allow backpacks into its theatre, and Oluniké would not leave her backpack for safekeeping with theatre staff. Theatre staff refused to sell her a ticket, and when she refused to leave, police were called. Adeliyi claimed she was discriminated against by the theatre staff, who filmed her, while the theatre staff claim they were following protocol. After police were called, Adeliyi was escorted out of the theatre. Adeliyi described the experience as "dehumanizing," and in an interview with the Toronto Star, she spoke further of the experience, saying:

In 2018 she received a Canadian Screen Award nomination for Best Supporting Actress at the 6th Canadian Screen Awards, for her role in the film Boost.