The Seniors Mental Health Policy Lens (SMHPL) is an analytical tool developed to identify unintended negative effects of current and planned policies, programs, and practices on seniors' mental health. It is designed (a) to promote social environments, including health services, supportive of older adults' mental health, and (b) to help ensure that the way mental health services are defined, delivered, and funded will result in increased emphasis on mental health promotion and on the prevention of mental health problems. The SMHPL incorporates Canadian seniors' perspectives on the factors influencing their mental health, and reflects the values of older adults.