Antonia Laura Thomas was born on 3 November 1986 in London, the daughter of a Jamaican mother and an English father. Her father is a classical bass singer. She studied for a Bachelor of Arts in acting at the Bristol Old Vic Theatre School, graduating in 2009, and then joined the National Youth Theatre.
Thomas was cast as Alisha Daniels in 2009, one day after leaving Bristol Old Vic Theatre School. She confirmed her exit from Misfits in late 2011, stating that she had an "amazing time" on the show. In 2012, she starred in the music video for the Coldplay song "Charlie Brown". In 2013, Thomas was in the film Sunshine on Leith. In 2014, she played the role of Evie in the British rom-com TV series Scrotal Recall which aired on Channel 4. After finding success on Netflix, the streaming network went on to commission a second series of 8 episodes, without Channel 4's involvement, which was made available globally on the streaming network in November 2016 under the new name Lovesick. In 2015, Thomas was featured in the Stereophonics song "C'est La Vie" and narrated the opening and closing lines to the reboot of the British children's television series Teletubbies. She is currently starring as a doctor the American TV show The Good Doctor.