Objective Vitamin D has been widely studied as a mediator of the immune response, becoming evident the prevalence of hypovitaminosis D in patients with Crohn's disease. This work aims at evaluating the serum levels of vitamin D in patients suffering from Crohn's disease in a southeast region of Brazil. Methods It is a prospective study, with statistical analysis of the values of serum vitamin D measured between April 2014 and April 2015 in patients with Crohn's disease. Individuals with mild anal complaints, without any colorectal involvement, comprised the control group. Results One hundred and four patients whose average age was 40.6 years were evaluated, being 56 (53.8%) female and 48 (46.2%) male. The average serum vitamin D level was 21.6 ng/mL, with standard deviation 13.85. The control group was comprised by 66 individuals, whose average age was 48.9 years. With 38 (57.6%) female and 28 (42.4%) male. In this group the average serum vitamin D level was 40.9 ng/mL. Statistical significance was demonstrated with p < 0.0001. Conclusion There was high prevalence of hypovitaminosis D in patients with Chron's disease, when compared to the control group. Hypovitaminosis D was not evidenced in patients in the latter group.