BackgroundConsiderable evidence supports the effectiveness of nutritional supplementation with or without nutrition education in preventing stunting in developing countries, but evidence from Afghanistan is scarce. ObjectiveThis project aimed to assess the effectiveness of specialized nutritious food (SNF), social and behavior change communication (SBCC) intervention to prevent stunting among children under 2 years during the first 1,000 days of life in Badakhshan, Afghanistan. MethodsWe used a community-based quasi-experimental pre-post study design with a control group. Pregnant and lactating women received a monthly ration of 7.5 kg of Super Cereal (250g/day) during pregnancy and the first 6 months of breastfeeding. Children aged 6-23 months received 30 sachets of medium-quantity lipid-based nutrient supplement (50g/sachet/day) monthly. We compared pre- and post-intervention assessments of the intervention and control groups to isolate the effect of the intervention on key study outcomes at the endline by difference-in-differences (DID) estimates. ResultsA total of 2,928 and 3,205 households were surveyed at baseline and endline. DID estimates adjusted for child, maternal, and household characteristics indicated a significant reduction in stunting (DID: -5% (95% CI: -9.9, -0.2) and underweight (DID: -4.6% (95% CI: -8.6, -0.5) among children <2 years of age. However, DID estimates for wasting among children in the intervention and control groups were not significantly different (DID: -1.7 (95% CI: -5.1,1.6). Furthermore, exposure to the SBCC messages was associated with improvements in the early initiation of breastfeeding (DID: 19.6% (95% CI: 15.6,23.6), exclusive breastfeeding under 6-months (DID: 11.0% (95% CI: 2.3,19.7), minimum meal frequency (MMF) (DID: 23% (95% CI: 17.7,28.2), minimum acceptable diet (MAD) (DID: 13% (95% CI: 9.8,16.3). ConclusionsThe provision of SNF in combination with SBCC during the first 1,000 days of life was associated with reduction in stunting and underweight and improvements in IYCF practices among children under 2 years of age. Clinical Trial Registry numberClinicaltrials.gov, NCT04581993.