Objective Insufficient levels of physical activity are a well-known modifiable risk factor for a number of chronic conditions including obesity, type 2 diabetes, cardiovascular diseases and certain malignancies. Little is known about the status of physical activity and its associated factors among adults in low-income countries, including Ethiopia. Therefore, this study aimed to assess the level of physical activity and its associated factors among adults in southeast Ethiopia.Design Analytical cross-sectional study.Setting Community setting in southeast Ethiopia.Participants 641 adults aged 18–64 years.Primary outcome Level of physical activity assessed via the Global Physical Activity Questionnaire (GPAQ).Results The overall prevalence of insufficient physical activity in this study was 29.48% (95% CI: 25.78 to 33.18). Women were more likely to report insufficient physical activity compared with men (39.0% for women and 12.3% for men, p<0.001). Being: a women (adjusted OR (AOR)=3.99, 95% CI: 2.15 to 7.40)), overweight/obese (AOR=1.95, 95% CI: 1.23 to 3.09), ever-married (AOR=2.13, 95% CI: 1.01 to 4.47), a person with no formal education (AOR=1.94, 95% CI: 1.05 to 3.56), a housewife (AOR=3.04, 95% CI: 1.75 to 5.29) and unemployed (AOR=3.30, 95% CI: 1.55 to 7.02) were significantly associated with insufficient physical activity.Conclusion The study revealed that three in 10 adults did not achieve the recommended level of physical activity. For chronic disease prevention in Ethiopia, the Ethiopian Ministry of Health and other stakeholders should pay special attention to strategies to improve the population’s physical activity especially among women, housewives, people with no formal education, and married, unemployed and overweight/obese adults.All data relevant to the study are included in the article or uploaded as supplementary information. All data generated or analysed during this study are included in this manuscript and its supplementary information files.