Abstract : Hypocalcemia is the most common complication after thyroidectomy operations. Our aim in this study is to investigate the relationship between hypocalcemia after total thyroidectomy and serum vitamin D levels. The study included of 100 consecutive patients who underwent total thyroidectomy. Patients had preoperative vitamin D levels <20 ng/ml [Group 1; n=50] and >20 ng/ml [Group 2; n=50] were divided into 2 groups. Groups were compared according to age, preoperative and postoperative corrected calcium and PTH levels. The mean vitamin D level was 12.4±3.8 ng/ml in group 1 and 31.2±7.5 ng/ml in group 2, and the vitamin D level was found to be significantly lower in group 1 compared to group 2 (p=0.0013). Preoperative serum Ca levels were found to be approximately the same in Group 1 and Group 2. When group 1 and group 2 were compared in terms of preoperative PTH values, mean serum PTH level (59.36±11.6 pg/ml) in group 1 was found to be significantly higher than group 2 (46.47±10.5 pg/ml) (p=0.001). In the postoperative period, the serum calcium level was below 8.5 mg/dl in 65 patients, and the postoperative hypocalcemia rate was 65%. The mean serum PTH levels after thyroidectomy were 59.12±8.66 pg/ml in all patient groups, and these values were significantly lower than the preoperative values (85.33±9.33 pg/ml) (p< 0.0001). When hypocalcemic and normocalcemic groups were compared, statistically significant difference was found between the two groups in terms of preoperative vitamin D levels (13.65±6.8 ng/ml vs 18.54±8.5 ng/ml, p=0.001). In our retrospective study, no significant effect of pre-surgery vitamin D deficiency on hypocalcemia after total thyroidectomy was found.