Early childhood development is becoming the focus of policy worldwide. However, the evidence on the effectiveness of scalable models is scant, particularly when it comes to infants in developing countries. In this paper, we describe and evaluate with a cluster-Randomized Controlled Trial an intervention designed to improve the quality of child stimulation within the context of an existing parenting program in Colombia, known as FAMI. The intervention improved children's development by 0.16 of a standard deviation (SD) and children's nutritional status, as reflected in a reduction of 5.8 percentage points of children whose height-for-age is below -1 SD. [Abstract copyright: © The Author(s) 2022. Published by Oxford University Press on behalf of European Economic Association.]