BACKGROUND: There are considerable socioeconomic inequalities in television-related sitting time, but there is little evidence for the explanatory mechanisms. We used a cohort of Belgian adults (25-60 years) and older adults (≥65 years) to examine the social cognitive, home environmental and health-related factors contributing to socioeconomic differences in television-related sitting. METHODS: We included 301 adults and 258 older adults (total n = 559). Linear regression analyses were used to examine the associations of education and occupational status with television-related sitting time, adjusted for age and gender. We assessed the explanatory power of social cognitive, home environmental and health-related factors using the traditional 'change-in-estimation method'. RESULTS: Those with low and medium education, respectively, engaged in 54 and 28 minutes per day more television-related sitting time than those with high education. We found no association between occupational status and television-related sitting time. Social cognitive factors explained 54% of the difference in television-related sitting time between those with low and high education, while home environmental factors only explained 6%, and health-related variables explained 10% of these differences. CONCLUSION: We found no occupational inequalities in television-related sitting time. Social cognitive variables such as attitude and modelling of the partner explained a large part of the educational inequalities in television-related sitting time. If confirmed by future studies, a focus on social cognition may help reduce sedentary behaviours in low-educated adults and diminish inequalities in sedentary behaviours.