Background: Cable cars are part of the transport system in multiple Latin American cities, but there are no evaluations of their effects on physical activity. TransMiCable, Bogotá's first cable car, includes complementary parks renovations. We assessed the effects of TransMiCable on physical activity. Methods: The natural experiment TrUST (Urban Transformations and Health) was conducted in 2018 and 2019 in intervention and control neighbourhoods. Physical activity was assessed before and after 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. Multilevel regression models were used to assess changes in physical activity. Findings: 40·5% of adults in the intervention group reported walking for transport more than 150 minutes per week before the TransMiCable and 51·6% afterwards (change 11·1%; 95% CI 6·4%, 15·9%), but this change did not differ from the control group (odds ratio 1·1; 95% CI 0·8, 1·5). Moderate-to-vigorous physical activity measured with accelerometry was 52·1 minutes per day before the TransMiCable and 59·4 minutes per day afterwards in new TransMiCable users (change 7·3; 95% CI -22·5, 7·9). Increased physical activity was observed in one of the parks in the intervention neighbourhoods, but only in males (odds ratio 2·7; 95% CI 1·1, 6·8). Interpretation: Physical activity remained high after a new transport mode in low-income neighbourhoods where walking is a necessity. Urban transport interventions should be accompanied by integral efforts to improve opportunities for active leisure.