Introduction. Calcific Tendinopathy (CT) of the shoulder is a common painful disorder. Due to the unknown etiology of CT, the present study aimed to evaluate possible relationship of serum calcium, phosphorus and vitamin D levels, history of calcium and vitamin D supplementation and incidence of CT. Methods. The present study is a case-control study which was performed on 38 patients with CT of the shoulder (n = 17) and the control group (n = 21). Data were recorded using a checklist including demographic information and serum levels of calcium, phosphorus and vitamin D and history of calcium and vitamin D supplementation. Data were analyzed by SPSS software version 21. Results. There was no significant difference between the two groups in terms of age and sex, history of calcium and vitamin D supplementation, serum calcium level, serum phosphorus level. There was a significant difference between the mean serum levels of vitamin D in patients with CT (P-value = 0.042). Conclusions. The results of the present study show a higher level of vitamin D in people with CT than the control group who were selected from normal people in the community.