After graduating, Black worked as a typist for a temp agency, a data entry clerk for the 1984 Summer Olympics and an usher in a Westwood movie theater. Eventually he asked for financial support of his parents during the six-month development of a script, The Shadow Company, a supernatural thriller set in Vietnam. With Dekker's help, the script landed him an agent and several lunch meetings with mid-level studio executives. This attracted 20th Century Fox executives, who were interested in having Black rewrite scripts. Eventually Black wrote an action film script, Lethal Weapon, in about six weeks, which landed him a $250,000 deal with Warner Bros. During the rewrites, Black asked Producer Joel Silver for a small acting role in another film Silver was preparing at the time, Predator, a film for which Black also made uncredited contributions to the script. At the same time, Black helped Dekker write The Monster Squad, which along with Lethal Weapon and Predator came out in 1987. Since then, Black has acted in five additional films and in two episodes for the TV series Dark Justice.

Black's next projects include an adaptation of Doc Savage, and The Destroyer, based on the 1985 film Remo Williams: The Adventure Begins, starring Fred Ward. He was also briefly attached by Warner Bros. in 2011, to direct a live-action American adaptation of the popular Japanese supernatural-thriller manga series: "Death Note", bringing his close collabrators: Anthony Bagarozzi and Charles Mondry to write the screenplay, replacing Charley and Vlas Parlapanides as the project's previous screenwriters. However, by 2014, he had quietly left the project, due to reported creative differences and other commitments. The studio had intended to omit "Shinigamis" (Japanese gods of death), who were originally present in the manga series, from the film's storyline, and revamp the main character: Light Yagami, into a more benelovent and sympathetic protagonist and change the story's moral theme of justice into one of vengeance, which Black had opposed, who intended to create a more faithful adaptation of the original manga. Adding to that, he decided to focus more on his "Doc Savage" and "Predator" projects, which resulted in his absence from the project's later developments and horror director: Adam Wingard being eventually hired to helm "Death Note" in 2015.

After living in the suburbs of Lower Burrell and Mount Lebanon, Pennsylvania, his family moved to Fullerton, California, during his sophomore year of high school. There he attended Sunny Hills High School and later UCLA where he majored in film and theater. While Black had a long history writing comic strips, short stories, and journalism, only during his senior year did he decide to make a living from it once his classmate Fred Dekker showed him a science fiction script he did for an assignment. Black's older brother Terry also wrote short stories and decided to move into screenplays starting with 1988's Dead Heat.

Feeling burned out and having conflicts with the studio, Black left the project after six months, earning only $125,000 (out of a $250,000 payment split with Murphy) for his work. After two sabbatical years, Black decided to take on an old idea of his that emerged during the production of Lethal Weapon and turn it into a full screenplay. The result, The Last Boy Scout, earned him $1.75 million in 1991. Black would also earn $1 million for his rewrite of Last Action Hero in 1993. He would set a record by receiving $4 million for writing The Long Kiss Goodnight in 1994.

Black made his directorial debut with 2005's Kiss Kiss Bang Bang, and later directed (and co-wrote with Drew Pearce) 2013's Iron Man 3, which ranks as the twelfth-highest-grossing film of all time worldwide.

Black received the Distinguished Screenwriter Award from the Austin Film Festival October 21, 2006. In 2005, he received the Best Original Screenplay award for Kiss Kiss Bang Bang from the San Diego Film Critics Association.

Black next directed the action comedy The Nice Guys, starring Russell Crowe and Ryan Gosling, and produced by Joel Silver. Warner Bros. handles North American rights to the film, which was released on May 20, 2016.

In June 2014, it was also announced that Black would co-write with Fred Dekker and direct alone the next film in the Predator series. The film will be titled The Predator and will be released on September 14, 2018.