Background: Augmentation mastopexy has undergone significant evolution over time. Despite advancements, traditional techniques often encounter challenges related to the durability of results and the maintenance of breast parenchymal stability. The multiplane L-scar augmentation mastopexy, incorporating a customized internal mastopexy, addresses these limitations by offering a targeted and reliable method to stabilize the parenchyma. Methods: This retrospective observational study analyzes a series of cases performed by the author between January of 2021 and December of 2023. Results: A total of 874 women underwent multiplane L-scar mastopexy, with a mean age of 37 years (range, 1 to 71 years). Follow-up durations ranged from 6 to 72 months. Complications related directly to the customized internal mastopexy were observed in 11.08% of cases, with the need for reoperation in 6% of patients. Conclusions: The customized internal mastopexy is a versatile and adaptable technique that enhances parenchymal stabilization and extends the durability of results in augmentation mastopexy. It can be seamlessly integrated into other mastopexy methods, offering a reliable solution to a critical challenge in breast surgery. Further studies comparing this technique with traditional methods are warranted to solidify its broader clinical utility.