As an amateur, Haney won seven National titles. In January 2015, aged 17, he became the youngest boxer to win the Youth World Championships in Reno. He had an amateur record of 138–8 bouts before turning professional in 2015 at the age of 17. Out of those eight losses, two are from his now rival Ryan Garcia in the amateurs the two have fought four times, both having won twice.
In April 2019, Haney signed a co-promotional deal between his own company, Devin Haney Promotions, and British promoter Eddie Hearn’s Matchroom Boxing. On May 25, 2019, Haney defeated Antonio Moran via a vicious seventh-round knockout, in his first match under the Matchroom banner.
On September 13, 2019, Haney defeated Zaur Abdullaev (11–0) to win the vacant WBC interim lightweight title.
In October 2019, Haney became the youngest (i.e. latest-born) world champion in boxing when he was elevated as the WBC lightweight champion after previous WBC lightweight champion Vasiliy Lomachenko was promoted to “Franchise Champion” by the WBC.
Haney was born in San Francisco and lived in Oakland, California as a child, but moved with his father Bill to Las Vegas. He started boxing at the age of seven. He converted to Islam in April 2021.