12 Years a Slave opened to wide acclaim, with many critics citing Ejiofor's performance and declaring him an almost-certain Academy Award nominee for Best Actor. From Owen Gleiberman at Entertainment Weekly: "It is Chiwetel Ejiofor's extraordinary performance that holds the movie together, and that allows us to watch it without blinking. He plays Solomon with a powerful inner strength, yet he never soft-pedals the silent nightmare that is Solomon's daily existence." From Christopher Orr at The Atlantic: "Ejiofor has given notable performances in the past (Dirty Pretty Things, Serenity, Talk to Me), but this is by far his most essential role to date. Stoic, watchful, compromising himself just enough to stay alive, he is the point of stillness and decency around which spin the madnesses of the film." In his The Hollywood Reporter review, Todd McCarthy wrote, "Ejiofor is terrific in a demanding character who's put through the wringer physically, mentally and emotionally." On 16 January 2014, Ejiofor was officially nominated for Best Actor for the 86th Academy Awards on 2 March.
In 2014, Ejiofor starred in the Nigerian film Half of a Yellow Sun alongside Thandie Newton.
It was announced in June 2014 that Ejiofor would play real-life drug dealer Thomas McFadden in film based on the book Marching Powder: A True Story of Friendship, Cocaine, and South America's Strangest Jail, written by McFadden and Australian journalist Rusty Young. In 2016, Ejiofor co-stars with his friend, Benedict Cumberbatch and played Baron Mordo in the Marvel film Doctor Strange. That same year, it was announced that he would play Peter in the upcoming film Mary Magdalene, written by Helen Edmundson and directed by Garth Davis. On 1 November 2017, he was officially chosen for the role of Scar for the computer animated remake, The Lion King (2019) directed by Jon Favreau. Played by Jeremy Irons in the 1994 animated film, Ejiofor described Scar as more "psychologically possessed" and "brutalized" than in the original. Ejiofor stated, "especially with Scar, whether it's a vocal quality that allows for a certain confidence or a certain aggression, to always know that at the end of it you're playing somebody who has the capacity to turn everything on its head in a split second with outrageous acts of violence – that can completely change the temperature of a scene." He also said that "[Scar and Mufasa's] relationship is completely destroyed and brutalized by Scar's way of thinking. He's possessed with this disease of his own ego and his own want." Favreau said of casting Ejiofor, "[He] is just a fantastic actor, who brings us a bit of the mid-Atlantic cadence and a new take on the character. He brings that feeling of a Shakespearean villain to bear because of his background as an actor. It's wonderful when you have somebody as experienced and seasoned as Chiwetel; he just breathes such wonderful life into this character." Ejiofor narrated the 2019 documentary film The Elephant Queen.