The Ciclov?a is a worldwide program in which streets are temporarily closed to motorized transport to create a space for recreation and outdoor play among children and adults. The aim of this study was to assess the associations between physical activity (PA), sedentary time (SED), body mass index and Ciclov?a participation among children aged 9 to 13 years. Methods All students in the 4th and 5th grades from the selected schools were invited to participate in the study. The study included 923 children. PA and SED were measured using waist-worn accelerometers, and height and weight were measured using standardized procedures. Ciclov?a participation was self-reported. The analyses included multilevel linear, generalized mixed and generalized additive models. Results The mean age of the sample was 10.1?0.7 years, and 49.5% were boys. In the last year, 46% of the children participated in the Ciclov?a, and 34% reported participating frequently (at least once per month). No differences were found in the mean minutes of moderate-to-vigorous PA on weekdays between frequent Ciclov?a users and sporadic and non-Ciclov?a users (72 vs 69; p = 0.09). In contrast, frequent Ciclov?a users had higher moderate-to-vigorous PA on Sundays than sporadic and non-Ciclov?a users (65.6 vs 59.2; p = 0.01), specifically between the hours of 12:00 and 16:00. In addition, frequent Ciclov?a users did not differ from the sporadic and non-Ciclov?a users in SED (515.3 vs 521.3; p = 0.19). Frequent Ciclov?a users had lower SED on Sundays than the sporadic and non-Ciclov?a users (437.7 vs 456.5; p = 0.005). Additionally, frequent Ciclov?a users were more likely to be overweight (28.3% vs 20.4% p = 0.01). We did not find differences in participation by sex, and low-to-middle income children were more likely to participate. Conclusions The Ciclov?as offer an innovative, inclusive recreational space and consequently provide opportunities to increase moderate-to-vigorous PA and reduce SED among children.