Background: Compared to other breast surgery methods, the accurate determination of pathologic margin in oncoplastic technique can affect its development and further employment of this technique. The current study aimed at evaluating positive pathologic margin after oncoplastic surgery and comparing it to that of the conventional breast-conserving surgery. Methods: The current cross sectional and prospective study enrolled patients with breast cancer referring to the surgical clinic of Tehran Cancer Institute from 2010 to 2013. In this study, patients with breast cancer were evaluated based on the type of surgery (oncoplastic or conventional breast-conserving) they had undergone. Accordingly, the positive or negative result of the margin surgery was compared between the groups. Results: In the current study, 317 patients with breast cancer underwent the surgery during the study period (154 patients in the oncoplastic and 163 patients in the conventional breast-conserving surgery groups). The highest frequency in the oncoplastic surgery belonged to Omega method (27.3%). The pathological evaluations after surgery showed ductal breast carcinoma in most of the cases in both groups (oncoplastic surgery = 94.2%; conventional breast-conserving surgery = 90.8%; P = 0.053). Positive margin in oncoplastic surgery and conventional breast-conserving surgery groups were 10.4% and 18.4%, respectively (P = 0.043). Among the 317 studied subjects, 14 relapse cases were observed; in 7 cases, mastectomy and in the rest, re-excision were conducted. Two out of 14 cases belonged to the positive margin group. Conclusions: Using oncoplastic surgery as a method for breast surgery may play an important role in reducing the prevalence of positive margins compared to the conventional breast-conserving surgery.