Background Those bereaved by suicide are a high-risk group of adverse health outcomes and suicidal behavior, yet little is known about the experiences and support needs of these individuals in the UK. Methods We conducted a national cross-sectional study using an online survey and analyzed the experiences of 7158 participants who had been bereaved or affected by suicide. Results Suicide had a major impact on 77% of participants, including those who had lost a friend and those exposed to suicide at a professional level. Mental and physical health problems linked to the suicide were reported in half. Adverse social outcomes and engaging in high-risk behaviors following the suicide were common. Over a third reported suicidal ideation and 8% had attempted suicide as a direct result of the suicide loss. Most had not accessed support services, with the majority viewing provision of local suicide bereavement support as inadequate. Conclusions Our results highlight the need for a multi-disciplinary approach in postvention and the provision of proactive outreach to support those bereaved by suicide. Postvention efforts need to acknowledge the death of a friend by suicide as a significant loss.