Physical inactivity is revealed as the global health problem that contributes to noncommunicable diseases (NCDs). High technological developments including smart phones or computers can cause of increased sedentary work and decreased leisure time of activities in healthy adults particularly in office workers. Sitting at desk or computer is routine in office workers. They did not require moderate or high physical workload. These caused of physical inactivity in office workers. Therefore, the facilitating factors or barriers related to physical activity (PA) participation should be identified. The purpose of this study was to assess the level of PA and to determine the facilitating factors and barriers associated to PA participation in office workers. Two study design were conducted: cross sectional survey and qualitative research. First, PA was collected by Thai version of short-form International Physical Activity Questionnaire (IPAQ). The participants were classified into high and low level of PA. Second, the facilitating factors and barriers of individual and environmental perspectives associated to PA participation in each level of PA were determined for 15-30 minutes. Data were analyzed by the descriptive statistics and content analysis. Our results found 18 of 22 office workers completed the IPAQ. Their mean ages were 32.61±4.62 years and spent 1585.89±1140.74 MET-min/wk. Of 18 office workers, 2 from low PA and 4 from moderate to high PA participated the in-depth interview. The health appearances and facilities could facilitate them to participate PA while lack of time and motivation were identified as the barriers. Our findings indicated the factors influenced on PA participation, therefore, it useful for planning the new strategy of PA promotion.