The objective was to examine the relationships of self-reported physical activity (PA) by domain (leisure, occupational, other) with PA and sedentary time as measured objectively by accelerometry. Subjects were adults with low habitual PA levels from a community in northern France. Among subjects in the lowest tertile of a PA score from a screening questionnaire, 160 (37% males, age: 41.0 ± 10.8 years, BMI: 25.1 ± 4.1 kg/m², mean ± SD) completed a detailed instrument (Modifiable Activity Questionnaire), and wore an accelerometer (Actigraph) for seven consecutive days. Relationships between questionnaire domains (occupational, leisure, and “non-occupational non-leisure”) and accelerometry measures (total activity and sedentary time) were assessed using Spearman correlation coefficients. In this population, the highest contributor to total reported PA (h/week) was occupational PA. Time spent in non-occupational non-leisure PA ranked second in women and third in men. The most frequent non-occupational non-leisure PA were shopping and household chores. In women, non-occupational non-leisure PA contributed more than occupational or leisure-time PA to total PA energy expenditure (median: 18.0, 9.1, and 4.9 MET-h/week, respectively). Total PA by accelerometry (count/day) was correlated to leisure-time PA in women (r = 0.22, P < 0.05) and to occupational (r = 0.43, P < 0.01) and total reported PA (r = 0.39, P < 0.01) in men (all in MET-h/week). There was an inverse relationship between accelerometry sedentary time (h/day) and non-occupational non-leisure PA (MET-h/week, r = −0.30, P < 0.001). These findings indicate the importance of assessing non-occupational non-leisure PA for a better understanding of how individuals partition their time between active or sedentary occupations.