The Mental Health Act 1983 was amended in 2007 and introduced the new role of the multidisciplinary Approved Mental Health Professional (AMHP) , who may be a nurse, psychologist, occupational therapist or social worker. The AMHP replaced the Approved Social Worker. Using a social constructionist perspective, this study has explored the decision-making of ten social work and ten nursing AMHPs in England. The purpose was to see if the decision making relating to management and assessment of risk varies according to the professional background of the AMHP. The study used an experimental vignette with each participant of audio-visual material containing mock health and social care records undertaken within a semi-structured interview. This study found that there was no difference in detention rates across the two groups studied in this research and found variance across the whole sample relating to the risks that were identified in the vignette. The findings suggest that there are differences in the way individual AMHPs reach decisions and in the factors that contribute towards that decision. Assumptions about discipline-related differences in social work and nurse decision-making have been challenged in this study. There is evidence to suggest that experience working in mental health was what AMHPs felt was the most significant factor contributing to their perception of risk. Overall, AMHPs expressed a good level of confidence in their practice as AMHPs. This study also highlighted that the majority of participants have felt afraid during a Mental Health Act assessment, and it illuminated how intuition and feelings have a role in how detention decisions are reached. The conclusion of this study gives rise to the need for further investigative research.