A cross-sectional province-wide survey study of 3,978 British Columbia (BC) nurses was conducted to explore the mental health state of the nursing workforce in BC. About one third of nurses reported depression and anxiety; about half reported symptoms of post-traumatic stress disorder and at least one third reported high levels of one or more dimensions of burnout. Mental health problems were about 1.5 to 3 times more prevalent among BC nurses compared to their peers nationally. Improving nurses' mental health requires multi-factorial and multi-level efforts. Evidence-based and workplace-specific policies and interventions that better support nurses at risk are recommended.