BACKGROUND: In patients with breast cancer for whom neoadjuvant chemotherapy (NAC) is planned, it is recommended to mark the primary tumor before treatment (planned surgery). However, surgeons may have to perform breast-conserving surgery on patients whose tumors are not marked (unplanned surgery). This study focused on the results obtained with planned and unplanned level II oncoplastic surgery (OPS) techniques applied to patients after NAC. METHODS: Patient groups who underwent planned, unplanned OPS and mastectomy after NAC were compared. Surgical margin status, re-operation and re-excision requirements, ipsilateral breast tumor recurrence (IBTR) and axillary recurrence rates recorded. Long-term local recurrence-free survival (LRFS), disease-free survival and overall survival were evaluated. RESULTS: There was no significant difference between the planned and unplanned OPS groups in terms of surgical margin status, re-excision requirement, and mastectomy rates. During an average follow-up period of 43 months, 5.3% and 4% of the patients in the planned OPS group developed IBTR and axillary recurrence, respectively, whereas these rates were 6.6% and 5.3% in the unplanned OPS group. In the mastectomy group, the rates of IBTR and axillary recurrence were found to be 4.1% and 3.8%, respectively. There was no significant difference between the three groups in terms of IBTR (p: 0.06) and axillary recurrence (p: 0.08) rates. CONCLUSION: Breast conserving surgery can be applied using level II OPS techniques with the post-NAC radiological examination and marking even if primary tumor marking is not done in the pre-NAC period.