Background Terrorist incidents lead to a range of mental health outcomes for people affected, sometimes extending years after the event. Secondary stressors can exacerbate them, and social support can provide mitigation and aid recovery. There is a need to better understand distress and mitigating factors among survivors of the Manchester Arena attack in 2017. Aims We explored three questions. First, what experiences of distress did participants report? Second, how might secondary stressors have influenced participants’ psychosocial recoveries? Third, what part has social support played in the relationships between distress and participants’ recovery trajectories? Method We conducted a cross-sectional online survey of a convenience sample of survivors of the Manchester Arena bombing (N = 84) in January 2021 (3 years 8 months post-incident), and a longitudinal study of the same participants’ scores on mental health measures over 3 years from September 2017. Results Survivors’ mental well-being scores in early 2021 were significantly lower than general population norms. Longitudinal follow-up provided evidence of enduring distress. Secondary stressors, specifically disruptions to close relationships, were associated with greater post-event distress and slower recovery. We found an indirect relationship between identifying with, and receiving support from, others present at the event and mental well-being >3 years later. Conclusions The Arena attack has had an enduring impact on mental health, even in survivors who had a mild response to the event. The quality of close relationships is pivotal to long-term outcome. Constructive support from family and friends, and people with shared experiences, are key to social cure processes that facilitate coping and recovery.