BACKGROUND: Provision of small-quantity lipid-based nutrient supplements (SQ-LNSs) during early life improves growth and development. In the International Lipid-Based Nutrient Supplements DYAD-Ghana trial, prenatal and postnatal SQ-LNS reduced social-emotional difficulties at age 5 y, with greater effects among children in less-enriched home environments. OBJECTIVES: We aimed to investigate the effect of prenatal and postnatal SQ-LNS on childrens social-emotional problems at age 9-11 y. METHODS: In 2009-2011, 1320 pregnant women ≤20 wk gestation were randomly assigned to receive the following daily until 6 mo postpartum: 1) iron and folic acid until delivery, then placebo, 2) multiple micronutrients (MMNs), or 3) SQ-LNS (20 g/d). Children in group 3 received SQ-LNS from 6 to 18 mo. In 2021, we evaluated childrens social-emotional outcomes with 6 assessment tools that used caregiver, teacher, and/or self-report to measure socioemotional difficulties, conduct problems, temperament, mood, anxiety, and emotion management. RESULTS: We assessed outcomes in 966 children, comprising 79.4% of 1217 participants eligible for re-enrolment. No significant differences were found between the SQ-LNS and control (non-LNS groups combined) groups. Few children (<2%) experienced high parent-reported social-emotional difficulties at 9-11 y, in contrast to the high prevalence at age 5 in this cohort (25%). Among children in less-enriched early childhood home environments, the SQ-LNS group had 0.37 SD (-0.04 to 0.82) lower self-reported conduct problems than the control group (P-interaction = 0.047). CONCLUSIONS: Overall positive effects of SQ-LNS on social-emotional development previously found at age 5 y are not sustained to age 9-11 y; however, there is some evidence of positive effects among children in less-enriched environments. The lack of effects may be owing to low prevalence of social-emotional problems at preadolescence, resulting in little potential to benefit from early nutritional intervention at this age in this outcome domain. Follow-up during adolescence, when social-emotional problems more typically onset, may yield further insights. This trial was registered at clinicaltrials.gov as NCT00970866. https://clinicaltrials.gov/ct2/show/record/NCT00970866.