In many centres, the myocutaneous transverse upper gracilis (TUG) flap represents an alternative choice in autologous breast reconstruction when abdominal tissue is unavailable. However, a single TUG flap may be volume deficient, particularly in the upper pole. We describe the application of simultaneous lipofilling to the pectoralis major muscle at the index procedure and present our decision-making algorithm, technique and outcomes. A retrospective review of all TUG flaps between January 2011 and May 2021 was conducted. Patient demographics, volume of primary and any subsequent fat grafting and complications were recorded. A total of 183 patients (242 TUG flaps) were included in this study. Of these; 130 patients were reconstructed with single TUG flaps, 16 patients received a single TUG flap with immediate lipofilling, and 37 patients underwent stacked, double TUG flap reconstructions. Of the 242 flaps, there were 2 flap losses (<1%), neither of which occurred in the immediate lipofilling cohort. Among the 130 single TUG patients, 28 (21.5%) required a cumulative total of 40, and a mean of 1.4, secondary lipofilling procedures. The immediate lipofilling patients were injected with a mean of 42 ml fat (range: 20-80 ml). In this group, only 2 of 16 patients required secondary lipofilling. The mean follow-up was 67 months (17-141). Primary lipofilling may reduce the need for secondary revisional procedures and appears safe at the index operation, adds little operative time and has negligible donor site morbidity. In patients where a second (stacked) flap would add unnecessary volume and complexity, it can be considered a useful adjunct.Copyright © 2023 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.