Improving infant and young child feeding (IYCF) has the potential to contribute to child development outcomes as well as nutrition. The Alive & Thrive (A&T) initiative in Bangladesh examined whether an intensive intervention package that was aimed at improving IYCF at scale also advanced language and gross motor development, and whether any advancements might be explained by improved complementary feeding. Results showed that the intensive IYCF intervention package, which provided mass media messages and community social mobilization along with intensive counseling delivered by trained and supervised frontline workers who received incentives for quality of performance, had a significant differential impact on language and gross motor development in comparison to the nonintensive intervention package. The path from the intensive intervention to advanced development was partially explained through improved complementary feeding and could have resulted from both biological (i.e., nutritional) and behavioral (i.e., caregiving) mechanisms. Further research may be helpful in understanding and potentiating these mechanisms. This research highlights the importance of measuring a diverse set of child outcomes, including functional outcomes for child development, when evaluating integrated nutrition programs.