Improved survival of preterm low birthweight (LBW) infants due to advances in neonatal care has brought issues such as postnatal development trajectories to the foreground. This study pools evidence from three cluster-randomized experiments evaluating community-based psychosocial stimulation programs conducted from 2014 to 2017 that included 3571 rural Chinese children aged 6-24 months (51.1% male, 96.2% Han Chinese). The risk of severe cognitive delay was found to be 26.5 percentage points higher for preterm LBW children than for their peers at age 2.5, with a prevalence rate of 48.3%. Results show that psychosocial stimulation interventions can improve child cognitive development at scale, with beneficial impacts on child cognition disproportionately larger for preterm LBW children, helping them to catch up developmentally.