Recognizing correlates of low physical activity (PA) can help in targeting PA interventions for individuals who would benefit most from increasing their PA. We studied the associations of demographic, social, health, and lifestyle factors with low PA by sex in a population sample of 1,303 Finnish individuals aged 57-78 years. We defined low PA as no moderate or vigorous leisure-time PA reported in an interview. Altogether, 39% of men and 48% of women reported low PA. Satisfactory or poor perceived health and high BMI were independently associated with low PA in both sexes. In men, factors such as age, being divorced or separated, still working, having a weak social network, poor diet, and a health professional's suggestion to increase PA were associated with low PA. In women, cardiovascular disease and depressive symptoms were associated with low PA. These results can be applied in targeting PA interventions.