Background Data on barriers to physical activity in older adults in Germany are scarce. The aim of this study was to analyse barriers to physical activity in a cohort of older adults, allowing comparisons between men and women, and age groups. Methods 1,937 older adults with a median age of 77 (range 72-93) years (53.3% female) took part in the 7-year follow-up telephone interviews of the getABI cohort. Participants who stated that they did not get enough physical activity were surveyed with respect to barriers to physical activity. Barriers were analysed for all respondents, as well as by sex and age group for cases with complete data. Multivariate logistic regression analysis was performed to evaluate differences between sexes and age groups. The level of significance (alpha < 0.05) was adjusted for multiple testing according to Bonferroni (p < .004). Results 1,607 (83.0%) participants stated that they were sufficiently physically active. 286 participants rated their physical activity as insufficient and responded to questions on barriers to physical activity completely. The three most frequently cited barriers were poor health (57.7%), lack of company (43.0%), and lack of interest (36.7%). Lack of opportunities for sports or leisure activities (30.3% vs. 15.6%), and lack of transport (29.0% vs. 7.1%) were more frequently stated by female respondents than male respondents. These differences between men and women were significant (p = .003; p < .001) after adjustment for respondents' age. Analyses by age groups revealed that poor health was more frequently considered a barrier to physical activity by participants aged 80+ years compared to the younger age group (71.1% vs. 51.5%). This age-dependent difference was significant (p = .002) irrespective of the participants' sex. Conclusions The present study provides relevant data on barriers to physical activity in older adults. By revealing appreciable differences between men and women, and age groups, this study has implications for efforts to increase older adults' physical activity. Promotion and intervention strategies should consider the barriers and tailor measures to the specific needs of older adults in order to reduce their constraints to physical activity.