Abstract Background Clinical emergency response systems such as medical emergency teams (MET) are used in many hospitals worldwide, but the effect that these systems have in mental health facilities is unknown. This study examined the rate and nature of MET calls to a mental health facility that had relocated to the campus of a tertiary referral hospital. Methods This study was a prospective, observational study of MET calls to a newly constructed 170 bed mental health facility. Data were collected on the number and nature of MET calls to the facility. Results Over 24 months, there were 66 MET calls to the mental health facility, and 1217 MET calls at the main hospital. The mean MET call rate was 14.2 calls per 1000 admissions (95% confidence interval (CI) 10.8–17.7) at the mental health facility, and 14.7 calls per 1000 admissions (95% CI 13.9–15.5) at the main hospital. Neurological and cardiovascular problems were present in 61% and 41% of MET calls. Conclusion The rate of MET calls to a new mental health facility can be similar to that of a tertiary hospital. Staff attending MET calls need to be prepared to manage predominantly neurological and cardiovascular problems.