We sought to (1) determine if there is an increased prevalence of vitamin D deficiency (VDD) in cases of sudden death in infancy and childhood; (2) establish whether there is a link between VDD and infection; and (3) assess if the level of vitamin D can be related to abnormalities in the skeletal survey and rib histology in our cohort. The postmortem reports of cases in which vitamin D levels were measured in 2009 and 2010 were retrieved. When parental consent for audit had been granted, rib histology and skeletal surveys were reviewed. Plasma 25-hydroxyvitamin D levels were measured in 41 postmortem cases. Ten (24.5%) had adequate levels, 5 (12%) had suboptimal levels, 16 (39%) had moderate deficiency, and 10 (24.5%) had severe deficiency. We had only 4 cases with VDD and infection. There were 25 cases of unexplained death in our cohort, and 76% of these had inadequate vitamin D levels. The rib histology was abnormal in 69% of cases that had inadequate vitamin D levels, while the radiology was abnormal in 19% of cases. A significant proportion of infants and children who died suddenly and unexpectedly had inadequate levels of vitamin D. We were unable to confirm or exclude an association between VDD and infection due to the small number of cases with confirmed infection. Further multicenter studies are needed to confirm our findings and explore possible associations between VDD and other known risk factors for sudden unexplained death in infancy and childhood.