Background: Undernutrition and poor cognitive development affect many children in developing countries. Good nutrition and health care are essential for optimal child development and growth. 

Objectives: We assessed the impact of peer counseling combined with psychosocial stimulation on feeding practices and child growth and development in slums in Bangladesh. 

Methods: We performed a community-based cluster randomized controlled trial in selected slums; 350 mother–infant pairs were allocated to receive peer counseling on feeding practices plus psychosocial stimulation (PC + PCS; n = 175) or usual health messages (control; n = 175) using restricted randomization. Data were collected at enrollment and 1, 3, 5, 7, 9, and 12 mo after delivery. We collected data on infant and young child feeding practices and anthropometric measurements from birth until 12 mo to assess the main outcomes, including feeding practices and growth. We used the Bayley Scale III at 12 mo to assess child development. The effects of the PC + PCS intervention were assessed by using regression models. 

Results: More mothers in the PC + PCS group than in the control group reported early initiation of breastfeeding (in the first hour: 89% compared with 78%, respectively; P < 0.05) and exclusive breastfeeding at 5 mo (73% compared with 27%, respectively; P < 0.001). Peer counseling had positively impacted infant length gain at 12 mo (P < 0.005). Children in the PC + PCS group were found to be more socially and emotionally active compared with controls at 12 mo (standardized score: 0.165 compared with −0.219, respectively; P < 0.05). 

Conclusion: Combining peer counseling with psychosocial stimulation had positive effects on infant feeding practices and growth at 12 mo and on the social–emotional development of young children. This trial was registered at clinicaltrial.gov as NCT03040375.