There are few prospective data on temporal trends in overall sitting time for different domains of sitting. This study examined time trends over 6 years in total and domain-specific sitting time in mid-age Australian men and women. Self-report data from 5246 participants in four survey waves (2007, 2009, 2011, 2013) of the HABITAT study in Brisbane, Australia, were analysed. Overall trends in ‘high’ total sitting time (>8 h/day sitting) and five domains were examined: a) >5 h/day for TV; b) >2 h/day for travel; c) >2 h/day for home computer use; d) >2 h/day for leisure; and e) >6 h/day for work. Sitting to watch TV and sitting at work accounted for more than half of total sitting time. The proportions who reported high sitting for computer use at home increased from 25% in 2007 to 37% in 2013 in men and from 19% to 29% over the same period in women. High TV sitting time was reported by 11.8% of men and 10.2% of women. These estimates increased to 16.5% and 13.2% respectively over the six years. In conclusion, although overall total sitting time remained fairly stable, there were significant increases in sitting time in some domains (home computer use and TV viewing) and in some sub-groups (such as women, and the employed). These increases were countered by declines in work-related sitting due to retirement.