Official police data from a Canadian city were used to provide insight into calls for police service that were primarily related to mental health concerns (N = 400). People with mental illness (PMI) consumer demographics, situation features, and outcomes of these interactions were analysed. Police encounters with PMI included youth and ethnic minorities, and were often characterized by substance abuse and self-harm. Over half of the encounters were resolved formally by police making Mental Health Act (MHA) apprehensions, though less than half of these apprehensions resulted in hospital admission. Indicators of PMI self-harm, abrupt cessation of medication by PMI, and police contact initiated by civilians or service providers (e.g. paramedics) increased the likelihood of MHA apprehensions. Police made mental health referrals during 40% of informally resolved incidents. Indicators of PMI self-harm, PMI ethnicity, and police contact initiated by service providers were predictors of police-initiated mental health service referral. Implications for police training and collaborations with mental health service providers are discussed.