Agnes O'Casey is best known as an actress in BBC's adaptation of Jo Bloom’s novel Ridley Road (2021), The Miracle Club (2023), Lies We Tell (2023), and various stage productions.

O'Casey was born Agnes Eustacia Kenig in London, England. She graudated from the Lir Academy, in Dublin. She is the great-granddaughter of playwright Seán O’Casey. In 2024 she won the award for Best Lead Actress in Film at the Irish Film & Television Awards for her work in Lies We Tell (2023).