Objective. To (1) compare occupational sitting between different socio-demographic, health-related, workrelated and psychosocial categories, (2) identity socio-demographic, health-related,work-related and psychosocial correlates of occupational sitting, and (3) examine the moderating effect of work-related factors in the relation between correlates and occupational sitting. Methods. Randomly-selected Australian adults completed a web-based survey assessing socio-demographic (country of birth, gender, age, education, income), health-related (general health, weight, physical activity), work-related (employment status, occupational task, occupational classification) and sedentary-specific psychosocial (social norm, social support, self-efficacy, control, advantages, disadvantage, intention) factors, and occupational sitting-time. t-tests, ANOVAs and multiple linear regression analyses were conducted (in 2013) on a sample of employees (n= 993). Results. Respondents sat on average for 3.75 (SD = 2.45) h/day during work. Investigated correlates explained 41% of the variance in occupational sitting. More occupational sitting was associated with being male, being younger, higher education and income, part-time and full-time employment, sedentary job tasks, white-collar/professional occupations, higher BMI, and perceiving more advantages of sitting less at work. Employment status and occupational classification moderated the association between control to sit less and occupational sitting. A lack of control to sit less was associated with higher occupational sitting in part-time and full-time workers, but not in casual workers; and in white-collar and professional workers, but not in bluecollar workers. Conclusions. Most important contributors to occupational sitting were work-related and socio-demographic correlates. More research is needed to confirm present results.