This study aimed to explore the trend in population levels, as well as the correlates, of occupational and leisure sitting time in full-time employed Australian adults between 2007 and 2015. We used data from the 2007/08, 2011/12 and 2014/15 Australian Health Surveys, in which nationally representative samples of the Australian population were interviewed. Full-time (≥35 hours/week) employed respondents reported sitting time at work and during leisure on a usual workday. Trends over time and associations between socio-demographic and health-related characteristics and sitting time were analysed in the combined dataset using multivariable logistic regression models. Over 21,000 observations were included in the analyses. Across the three surveys, approximately 51% of the respondents reported ≥4 hours/workday occupational sitting time, 40% reported ≥4 hours/workday leisure sitting time, and 55% reported ≥7 hours/workday combined occupational and leisure sitting time. There were no clear trends over time. All potential correlates were associated with occupational sitting time and all but educational level were associated with leisure sitting time. The directions of the associations with gender, age and leisure-time physical activity were reversed for occupational sitting time and leisure sitting time. These findings show that the average levels of occupational and leisure sitting time on workdays were high but stable over the past decade. The observed differences in correlates of occupational and leisure sitting time demonstrate the need to assess and address sedentary behaviour domains separately in research and policy.