Background: Cable cars are part of the transport system in several cities in Latin America, but there are no evaluations of their effects on physical activity. TransMiCable is the first cable car in Bogotá and the intervention includes renovated parks and playgrounds. We assessed the effects of TransMiCable on physical activity.Methods: The Urban Transformations and Health (TrUST) natural experiment was conducted in 2018 and 2019 in intervention and control neighbourhoods. Physical activity was assessed before and after the intervention using questionnaires (825 and 854 adults in the intervention and control groups) and accelerometers (357 and 334 adults in the intervention and control groups). Physical activity was also assessed using direct observation in parks and playgrounds. Multilevel regression models were used to assess changes in physical activity.Findings: 40.5% of adults in the intervention group reported more than 150 minutes per week of walking for transport before the intervention and 52% afterwards (95% confidence interval for the change: 6%, 16%). Similar changes were observed in the control group. Moderate-to-vigorous physical activity measured using accelerometers was 52.1 minutes per day before and 59.4 minutes per day after the inauguration in new users (change: 7.3; 95% confidence interval: -22.5, 7.9). An increase in physical activity was observed in one of the renovated parks, but only in males (odds ratio versus control parks: 2.7; 95% confidence interval: 1.1, 6.8).Interpretation: It is encouraging that walking for transport remained high in the intervention neighbourhoods when people elsewhere in Bogotá were turning to motorized transport.Funding: Wellcome Trust (as part of SALURBAL project), Bogotá Urban Planning Department, MinCiencias, Universidad de Los Andes, Fundación Santa Fe de Bogotá, Universidad del Norte.Declaration of Interest: The authors declare no competing interests.Ethical Approval: The study was approved by the ethics committee of Universidad de Los Andes (Acta No. 806-2017; Acta No. 977-2019; Acta No. 994-2019). All participants provided written informed consent.