He has written a series of best-selling historical mysteries featuring the hard-boiled detective Easy Rawlins, a black private investigator living in the Watts neighborhood of Los Angeles, California.

[2] His father, Leroy Mosley (1924–1993), was an African American from Louisiana who was a supervising custodian at a Los Angeles public school.

[7] Mosley describes his father as a deep thinker and storyteller, a "black Socrates.” His mother encouraged him to read European classics, from Dickens and Zola to Camus.

While working for Mobil Oil, Mosley took a writing course at City College in Harlem, after being inspired by Alice Walker's book The Color Purple.

[9] One of his tutors, there, Irish writer Edna O'Brien, became a mentor and encouraged him, saying: "You're Black, Jewish, with a poor upbringing; there are riches, therein.

Mosley's first published book, Devil in a Blue Dress, was the basis of a 1995 movie starring Denzel Washington, and the following year, a 10-part abridgement of the novel by Margaret Busby, read by Paul Winfield, was broadcast on BBC Radio 4.

[11] The world premiere of Mosley's first play, The Fall of Heaven,[12] was staged at the Playhouse in the Park, Cincinnati, Ohio, in January 2010.

"[9] In 2019, after working in the writers room for the television series Snowfall, Mosley was hired, by Alex Kurtzman, for a similar role on the third season of Star Trek: Discovery.

Mosley chose to leave the series, quitting without informing Kurtzman, and he explained his decision in an op-ed for The New York Times, in September 2019.