OBJECTIVES:This article examines relationships between experiences of ageism and four specific mental health outcomes among older Australian adults, including whether these relationships vary depending on age, gender, and sexual orientation. METHODS:A survey was conducted nationwide involving 2137 participants aged 60 years and older. Mental health variables included depressive symptoms, anxious symptoms, general stress, and positive mental health or flourishing. RESULTS:Recent experiences of ageism were found to be strongly related to poorer mental health on all four mental health variables. However, experiences of ageism appeared to have a greater effect on the mental health of those who were younger in age (specifically depression), of men more so than women (specifically depression), and of those who identified as heterosexual as opposed to other sexual orientations (specifically general stress). CONCLUSION:These findings suggest that experiences of ageism may be an important factor in the health and well-being of older adults, especially for those who are younger, male, and heterosexual, and may need to be taken into account when devising strategies for supporting healthier and happier ageing.