Risk assessments are a central component of mental health care. Few national studies have been done in the UK on risk assessment tools used in mental health services. We aimed to examine which suicide risk assessment tools are in use in the UK; establish the views of clinicians, carers, and service users on the use of these tools; and identify how risk assessment tools have been used with mental health patients before suicide.We did a mixed-methods study involving three components: collection and content analysis of risk assessment tools used by UK mental health services; an online survey of clinicians, service-users, and carers; and qualitative telephone interviews with clinicians on their use of risk assessment tools before a suicide death and their views of these tools. The online survey was advertised through the National Confidential Inquiry into Suicide and Safety in Mental Health's (NCISH) website and social media, and it included both quantitative and open-ended qualitative questions, and respondents were recruited through convenience sampling. For the telephone interviews, we examined the NCISH database to identify clinicians who had been responsible for the care of a patient who died by suicide and who had been viewed as being at low or no immediate risk of suicide.We obtained 156 risk assessment tools from all 85 National Health Service mental health organisations in the UK, and 85 (one per each organisation) were included in the analysis. We found little consistency in use of these instruments, with 33 (39%) of 85 organisations using locally developed tools. Most tools aimed to predict self-harm or suicidal behaviour (84 [99%] of 85), and scores were used to determine management decisions (80 [94%]). Clinicians described positive aspects of risk tools (facilitating communication and enhancing therapeutic relationships) but also expressed negative views (inadequate training in the use of tools and their time-consuming nature). Both patients and carers reported some positive views, but also emphasised little involvement during risk assessment, and a lack of clarity on what to do in a crisis.Assessment processes need to be consistent across mental health services and include adequate training on how to assess, formulate, and manage suicide risk. An emphasis on patient and carer involvement is needed. In line with national guidance, risk assessment should not be seen as a way to predict future behaviour and should not be used as a means of allocating treatment. Management plans should be personalised and collaboratively developed with patients and their families and carers.The Healthcare Quality Improvement Partnership.