Objectives This study aims to compare the developmental profile of severe acute malnourished (SAM) and normal under-five children and to find sociodemographic determinants accountable for their developmental disabilities. Setting We conducted a multi-centre cross-sectional study in three basic health units and one rural health centre in Pakistan. Participants 200 children (SAM and healthy) aged 6–59 months. Primary and secondary measures We screened for nutritional status and clinical complications. Children underwent for developmental assessment by Denver Development Screening Tool II. A pretested structured questionnaire on sociodemographic characteristics and nutrition was used for collecting data about determinants of developmental delay. Results We observed statistically significant differences in anthropometric measurements among SAM compared with normal nourished in weight, height, mid-upper arm circumference and weight-for-height z-scores. SAM serves as a significant risk factors (p<0.001) for delayed personal or social development (69% vs 11%; OR (95% CI)=18.01 (8.45 to 38.37)), delayed fine motor development (39% vs 8%; OR (95% CI)=7.35 (3.22 to 16.81)), delayed language development (32% vs 8%; OR (95% CI)=5.41 (2.35 to 12.48)), delayed gross motor development (34% vs 10%; OR (95% CI)=4.64 (2.14 to 10.05)) and delayed global development (66% vs 20%; OR (95% CI)=7.77 (4.09 to 14.74)). Applying logistic regression, personal or social development (p<0.001) and language development (p<0.05), under-five siblings was a risk factor, while among gross motor development, mother’s educational status (p<0.05) was a significant risk factor for developmental delay. Conclusions Our analysis indicates that children with malnutrition have a high frequency of developmental delays. Missing maternal education and a higher number of under-five siblings are also potential risk factors for developmental delay.