BACKGROUND: Children with obesity frequently have functional impairment after critical illness. Although obesity increases morbidity risk after trauma, the association with functional outcomes in children is unknown. OBJECTIVE: To evaluate the association of weight with functional impairment at hospital discharge in children with serious injuries. METHODS: This secondary analysis of a multicenter prospective study included children <15 years old with a serious injury. Four weight groups, underweight, healthy weight, overweight, and obesity/severe obesity were defined by body mass index z-scores. The functional status scale (FSS) measured impairment across six functional domains before injury and at hospital discharge. New domain morbidity was defined as a change ≥2 points. The association between weight and functional impairment was determined using logistic regression adjusting for demographics, physiological measures, injury details, presence of a severe head injury, and physical abuse. RESULTS: Although most patients discharged with good/unchanged functional status, new domain morbidity occurred in 74 patients (17%). New FSS domain morbidity occurred in 13% of underweight, 14% of healthy weight, 15% of overweight, and 26% of obese/severe obese patients. Compared to healthy weight patients, those with obesity had more frequent new domain morbidity (p = 0.01), while the other weight groups had similar morbidity. However, after adjustment for confounders, weight was not associated with new functional morbidity at discharge. CONCLUSION: Patients with obesity have greater frequency of new domain morbidity after a serious injury; however, after accounting for injury characteristics, weight group is not independently associated with new functional morbidity at hospital discharge after injury in children. LEVEL OF EVIDENCE: III.