Prisoners with mental illness on release from prison often face complex challenges with little support, leading to poor clinical and social outcomes. This feasibility study aimed to see whether a Critical Time Intervention (CTI) in the first weeks post-release effectively connects mentally ill prisoners with social, clinical, housing, and welfare services on leaving prison. The study took place in 2007 and involved local prisons in London and Manchester. A pilot randomised controlled trial in which CTI was compared to Treatment as Usual (TAU). Sixty prisoners were randomised in the trial, with outcome measures completed on 23. A higher proportion of prisoners in CTI group were in contact with services at follow-up than those receiving TAU. CTI prisoners were significantly more likely to be receiving medication, and be registered with a General Practitioner (GP) than those in the TAU group. Continuity of care for prisoners with severe mental illness can be improved by working with them to identify their needs prior to release, and by assisting them to engage effectively to the necessary agencies in the community.