Background: Multinodular goiter (MNG) is a common disease in Pakistan. However, malignancy can be found occasionally on histopathological examination of resected goiter specimens. The objective of this study was to determine the frequency of malignant lesions on histopathological examination in thyroid specimens operated for multinodular goiter.Material and Methods: A total of 154 patients undergoing thyroid surgery with preoperative diagnosis of multinodular goiter (MNG) at Al Nafees Medical College and Hospital Islamabad, Pakistan were included in this study. The preoperative diagnosis of MNG was made upon physical examination of thyroid and ultrasound (n=62 cases) and FNAC (n=43 cases) was done in selected cases. Gross examination was done and sections were taken from areas of thyroid with varied appearances including hemorrhagic, solid, firm, white, gray, gelatinous as well as necrotic areas. Qualitative variables, were calculated in terms of percentages and mean and standard deviation were used for quantitative variables.Results: Of the 154 patients with preoperative diagnosis of MNG, there were 139 (90%) female and only 15 (10%) male patients. The age range was 14-60 years with a mean age of 36 ± 10 years The incidence of thyroid carcinoma in patients operated for clinical diagnosis of MNG was 8% (n=12). Papillary thyroid carcinoma was the most frequent type of malignancy (83.3%; n=10). Multifocality (60%; n=6), bilaterality (33.3%; n=4) and left lobe involvement (80%; n=8) of thyroid were more common. Microcarcinoma (measuring 1cm or less) was found in 50% (n=5) of these PTC. Histological type of papillary carcinomas greater than 1 cm were follicular variant (n=3; 30%) and conventional (n=2; 20%) types. The maximum measurement of the tumor was 2 cm. In all cases of PTC, rest of the thyroid showed MNG on histopathology.Conclusions: Incidental finding of thyroid malignancy in clinically diagnosed cases of MNG is not unusual. Papillary carcinoma of thyroid is the most common incidental malignant finding in these cases. Multilocularity in thyroid is not an indicator of benign disease process.