There is a growing body of evidence that higher level of physical activity is associated with a better state of mental health. Less is known about the relationships between youth competitive sports and mental health in the adulthood. The aim of the study was to examine whether retrospectively assessed sports participation (SP) and competitive sports (CS) at the age of 12 years is associated with mental health (mental well-being as well as mental distress) and health behaviour in young adulthood among males. The study sample consisted of 680 males aged between 20−35 years. The data were gathered with self-administered questionnaires in 2015 in Finland. Mental well-being was measured with The Short Warwick-Edinburgh Mental Well-Being Scale and mental distress with five items of SF-36 scale. SP at the age of 12 is associated with better mental health in young adulthood, with both mental well-being (OR=1,86, 95 % CI 1.11−3.11) as well as mental distress (OR=0.61, 0.41−0.90). Age, years of education and current physical activity were controlled. Higher level of intensity of SP or the level of CS in childhood was associated with lower level of mental distress in adulthood. No association was found between the level of CS in childhood and mental well-being in adulthood. Further, the study showed that youth SP can present a higher risk for increased alcohol consumption and use of snuff and tobacco in adulthood. Despite negative outcomes related to health behaviour, the findings provide support for the association between youth sports participation and mental health outcomes in adulthood among males.