Radioactive premiered as the Closing Night Gala at the Toronto International Film Festival on 14 September 2019. To celebrate International Women's Day, the film's UK premiere took place at the Curzon Mayfair Cinema on 8 March 2020, ahead of its intended 20 March theatrical release, which was cancelled due to the COVID-19 pandemic. StudioCanal eventually released the film in the United Kingdom through electronic sell-through platforms on 15 June 2020 and through video on demand on 6 July, followed by a DVD release on 27 July. In the United States, where the film was originally set to be released theatrically on 24 April 2020 by Amazon Studios, it was released straight to Amazon Prime Video on 24 July 2020.