Familial mediterranean fever (FMF) is an autosomal recessive disorder caused by mutations in the FMF gene (MEFV). The gene causing FMF, designated MEFV, encodes a protein called pyrin or marenostrin that is expressed mainly in myeloid bone marrow precursors, neutrophils, and monocytes. Since there are several etiological factors, FMF is the most common periodic fever syndrome. However, it is still unknown what triggers or ends these periodical attacks. As a pleiotropic hormone, vitamin D has immunomodulation effects. The aim of this study was to evaluate the vitamin D levels in FMF patients. The study group was comprised of 26 patients diagnosed with FMF (men/women: 12/14), and 34 healthy control (men/women: 17/17). Vitamin D levels in FMF patients and healthy controls were 11.05 ± 7.11, 17.15 ± 6.49, respectively. FMF patients had significantly decreased vitamin D levels compared with healthy controls (P < 0.001). In conclusion, it is thought that vitamin D deficiency in FMF patients may trigger the attacks. Further studies with larger patient populations need to hold to investigate the vitamin D deficiency in patients with FMF and that may assist to clarify the mechanism behind the colchicines resistant cases.