In the context of decreased access to inpatient mental health care, the assessment of risk behavior in older adults living in the community is a growing concern. The purpose of the study was to develop a risk behavior screening tool to help community practitioners plan early intervention for frail older adults with severe mental illness (SMI) referred to community health and social service centers. The initial instrument development involved discussion-based work among practitioners and researchers. It was followed by a content validation phase (involving nine experts), preliminary testing of inter-rater reliability (27 subjects, 12 pairs of raters), and item analysis procedures combining previous data. The psychogeriatric and risk behavior assessment scale (PARBAS) includes 34 items organized in 10 sections of risk behavior: (i) self neglect; (ii) non-compliance; (iii) substance abuse; (iv) risk toward oneself and others; (v) aggressive behavior; (vi) emotional distress; (vii) suicidal behavior; (viii) personal security; (ix) risk of victimization by others and (x) financial security. It can provide professionals with essential information about their clients' risky behaviors, thereby contributing to timely and appropriate preventive interventions. Future research is needed to establish its psychometric properties.