Breast-conserving surgery (BCS) followed by radiotherapy is preferred for early-stage breast cancer because its survival rate is equivalent to that of mastectomy. Achieving negative surgical margins in BCS is crucial to minimize the risk of recurrence. Intraoperative ultrasound (IOUS) enhances surgical accuracy, but its efficacy is operator dependent. This study aimed to compare the success of achieving negative margins using IOUS between an experienced breast surgeon and general surgical residents and to evaluate the learning curve for the residents. A prospective study involving 96 patients with BCS who underwent IOUS guidance was conducted. Both the breast surgeon and residents assessed the surgical margins using IOUS, with the breast surgeon making the final margin adequacy decision. Permanent histopathological analysis was used to confirm the status of the margins and was considered the gold standard for comparison. The breast surgeon accurately assessed the margin status in all 96 cases (100% accuracy), with 93 negative and three positive margins. All of these were ductal carcinomas in situ. Initially, the residents demonstrated low accuracy rates in predicting margin positivity using intraoperative ultrasonography. However, the learning curves of the three residents demonstrated that, with an average 12th case onwards, a significant improvement in the cumulative accuracy rates was observed, which reached the level of the breast surgeon. IOUS is an effective tool for accurately predicting the margin status in BCS, with an acceptable learning curve for novice surgeons. Training and experience are pivotal for optimizing surgical outcomes. These findings support the integration of IOUS training into surgical education programs to enhance proficiency and improve patient outcomes.