Background: Coronavirus disease 19 (COVID-19) has compelled implementing confinement measure across the globe. These measures can potentially lead to many changes in lifestyle. However, no studies examined the effect of COVID-19-induced confinement on physical activity (PA) and sedentary behavior (SB). Methods: During April and May of 2020, the current study surveyed changes in PA and SB induced by COVID-19 confinement. Results: The participants of the study were 1844. Among the participants who were regularly involved in PA, the majority (41.8-42.2%) of the participants reported a "decrease" (p<0.05) in walking, jogging, and sports while the majority (46.3-53.1%) reported a "no change" (p<0.05) in swimming, cycling, and weight lifting. With regard to the SB, most of the participants reported an "increase" in watching TV (72.3%), using electronics (82.7%), and logging to social media (81.9%). Additionally, gender, job type, obesity, and being worried to contract the disease were associated (p<0.05) with changes in PA. On the other hand, age, gender, obesity, job type and income were related (p<0.05) to changes in SB. Conclusion: Results of the current study might enhance knowledge about the impact of COVID-19 on lifestyle, particularly PA and SB. Subsequently, it can also be used to establish strategies to enhance engagement in activities during the current and future pandemics.