Oncoplastic techniques in breast cancer treatment allow increasing indications of breast-conserving surgery and improving cosmetic results. Breast tumors located at the superior edge of the upper quadrant or at the upper inner quadrant represent a challenge for conservative surgery due to insufficient breast thickness and risk of skin involvement. We present a modified Burow's triangle advancement flap for breast-conserving surgery in patients with breast tumors at these locations. This retrospective observational study analyzed 8 out of 213 patients submitted to major oncoplastic breast procedures, who underwent breast-conserving surgery with matrix rotation mammaplasty, using a modified Burow's triangle advancement flap. All patients were treated in public and private health systems in Santiago, Chile. The median age at diagnosis was 47 years. The average initial tumor size was 5.9 cm, and the mean excised breast weight was 117 g. Patients required neither symmetrization nor displacement of the nipple-areola complex. Only one patient had a minor complication (wound dehiscence). During follow-up, no local recurrences were reported. We conclude that the modified Burow's triangle advancement flap is a safe and effective technique to manage tumors at this complex location. It provides adequate oncological margins, good cosmetic results, and contralateral symmetry, with complication rates similar to those of standard conservative surgery.