We aimed to examine the prevalence and correlates of opportunistic skin check behaviours among Australians and whether changes over time might explain increasing underlying rates of melanoma in situ. The National Sun Protection Survey involved periodic telephone-based cross-sectional surveys during summer since 2003. Skin checks by a doctor in the past 12 months was asked in four summers over 2006-2017, and responses from 23,374 Australians aged 12-69 years were analysed. Prevalence estimates were weighted to be representative of the Australian population. Chi-square tests compared the prevalence over time and by characteristics. The overall proportion reporting whole-body skin checks in the past 12 months was 20 % in 2006-07 and 2010-11, 21 % in 2013-14, and 22 % in 2016-17; but increased from 29 % in 2006-07 to 37 % in 2016-17 for those aged 45-69 years (p < 0.0001). In 2016-17, 5% reported a skin check of part-body and 9% for a specific mole or spot. The proportion reporting no skin checks increased from 61 % to 64 % over time (p < 0.0001). Whole-body skin checks were more common among older respondents, females, and also varied by residence location, skin sensitivity, skin colour, risk perception, and socio-economic index (all p < 0.001). Approximately one third of Australians had their skin checked by a doctor within a 12-month period, but this varied across population sub-groups. Skin check behaviours were relatively stable over time, with modest increases in the prevalence of skin checks for those aged 45-69 years. These findings do not explain underlying large increases in rates of melanoma in situ.