Aims: Physical inactivity in adolescents is a global health problem. Eighty percent of adolescents worldwide do not meet the minimum recommended physical activity. Although many adolescents define themselves as a ‘sports fan’, the relationships between sports spectatorship and sport participation in adolescents have not yet been investigated. Here, we determine whether there is a relationship between the levels of sports spectatorship and physical activity among adolescents. Methods: The Physical Activity Questionnaire for Adolescents (PAQ-A), Sport Spectator Identification Scale (SSIS) and three questions regarding total screen time spent watching a sports game and other sports-related screen time on weekdays and weekends were given to high school students in two cities in Turkey (Konya and Ankara). Results: After excluding 21 invalid questionnaires, a total of 1100 full and valid questionnaires were returned from the participants (578 females, 522 males). Participants were aged between 13 and 19 (median = 15) years. Female students had lower PAQ-A (median = 2.38, interquartile range (IQR) = 0.99) and SSIS scores (median = 19, IQR = 24) and less total screen time on weekends compared to male students (median PAQ-A = 2.64, IQR = 1.05; median SSIS = 29, IQR = 30) ( p < .05). The physical activity level of the students was significantly lower among those at higher grades. A weak positive correlation was found between SSIS scores and PAQ-A scores ( r = .28, p < .01). Multiple linear regression analysis revealed that sex, age and SSIS scores were all significant predictors of PAQ-A scores ( p < .001). Conclusions: When comparing female and male adolescents, we found that females scored significantly less in mean physical activity levels, screen time on weekends and sports spectator identification. A positive correlation was observed between sports spectator identification and physical activity levels, both in males and in females. Higher sports spectator identification, being younger and being male were all significant predictors of higher levels of physical activity.