Rainwater tanks or cisterns are a low impact development infrastructure used to control stormwater runoff and reduce water demand. However, climate change may affect its performance due to increased rainfall intensities. This study evaluates the uncertainty on the effectiveness of cisterns to reduce peak runoff under climate change in an urban watershed in Brazil. Twelve updated intensity-durationfrequency curves, based on six Global Circulation Models and two Representative Concentration Pathways (RCP 4.5 and RCP 8.5) from the Coupled Model Inter-comparison Project 5, were used to yield hyetographs for 2 h-storm events with different recurrence intervals. Peak runoff reduction ranged between 0.4% and 5.5% for RCP 4.5 and 0.4% and 6.3% for RCP 8.5. Under climate change, a reasonable runoff control could be reached if at least 20% of the buildings installed a 5 m3 cistern. Uncertainty in future climate should be addressed in rainfall-runoff modelling to guide stormwater management decisions.