BACKGROUND: Research describing the splenic capsule and its effect on non-operative management of splenic injuries is limited. The aim of this study is to identify the current beliefs about the splenic capsule thickness and investigate changes in the splenic capsule with age. METHODS: Trauma Medical Directors were surveyed on their beliefs regarding splenic capsule thickness changes with age. Thicknesses of cadaveric splenic capsule samples were measured. RESULTS: The majority of trauma medical directors (59%) believe the capsule thickness decreases with age. There were 94 splenic specimens obtained. The splenic capsules of infants were thin and had a uniform layer of elastin fibers. With aging, the capsule becomes thick and develops a collagen layer. CONCLUSION: Most trauma directors believe the splenic capsule thickness decreases with age. However, our results demonstrate that the splenic capsule thickness increases during childhood but remains constant in adulthood.