Aim A 2016 Cochrane review showed that Kangaroo mother care (KMC) had a moderate impact on preterm growth, with high heterogeneity among studies. This systematic review and meta‐analysis considered new evidence on KMC, particularly the duration. Method Databases were searched for papers published in English, French, Spanish and Portuguese up to 2017. Randomised controlled trials (RCT) of preterm or low birth weight infants were included if they compared growth between KMC and conventional care. Anthropometric measures were related to duration. Results We identified 1368 papers, and 13 RCTs covering 743 KMC infants and 718 controls met the selection criteria. Infants held in KMC for at least 6 h/d gained more weight than the controls, with a mean difference of 8.99 g/d (95% confidence interval 8.14‐9.84, I2 = 0%). This difference persisted between 2 and 6 h/d and disappeared with 2 hours or less. When we used g/kg/d, the weight gain was higher when the duration was at least 8 h/d. Only babies who received 6 h/d gained more length and head circumference. Conclusions The effect of the KMC on growth was directly related to the duration.