To identify incidence, preoperative features, surgical factors, and postoperative events of incidental parathyroidectomy (IP) during thyroidectomy. A total of 1068 consecutive patients who underwent thyroidectomy performed by a single surgeon between January 2003 and April 2012 were enrolled in retrospective study with prospectively collected data. University hospital. To assess the impact of IP on study variables, patients were stratified into 2 study groups: IP group and non-IP group. Univariate and multivariate analyses identified significant correlates of IP. In all, 5.4% patients experienced IP. Significant difference (P < .001) was in incidence of temporary hypocalcemia between IP group (36.2%) and non-IP group (16.8%). Multivariable logistic regression model identified total thyroidectomy (odds ratio 3.937, 95% confidence interval [CI] 1.462-10.601, P = .007) and Graves' disease (odds ratio 2.192, 95% CI 1.157-4.158, P = .016) as risk-adjusted factors associated with IP. Multivariate analysis of repeated measures identified statistically significant difference of repeated total calcium level (P < .001) and ionized calcium level (P = .020) between study groups. IP during thyroidectomy might be potential complication. Total thyroidectomy, Graves' disease, longer operation time, and identification 3 and more parathyroid glands seemed to be predictive factors for IP. IP is significantly associated with temporary hypocalcemia, but not with permanent hypoparathyroidism.