Skin incision scars are cosmetically displeasing; the effects of current treatments are limited, and new methods to reduce scar formation need to be found. We sought to determine whether immediate postoperative injection of stromal vascular fraction gel (SVF-gel) could reduce scar formation at skin incision sites. A prospective, randomized, double-blind, self-controlled trial was conducted in patients who underwent breast reduction. SVF-gel was intradermally injected into the surgical incision on one randomly selected side, with the other side receiving saline as a control. At the 6-month follow-up, the incision scars were evaluated using the Vancouver scar scale (VSS) and visual analog scale (VAS). Antera 3D camera was used for objective evaluation. The VSS score and VAS score were significantly different between the SVF-gel-treated side (3.80 ± 1.37, 3.37±1.25) and the control side (5.25 ± 1.18, 4.94 ± 1.28). Moreover, the SVF-gel-treated side showed statistically significant improvements in scar appearance, based on evidences from Antera 3D camera. This was a single-center, single-race, and single-gender study. Furthermore, the results were available only for the 6-month interim follow-up period. Postoperative immediate SVF-gel injection in surgical incisions can reduce scar formation, and exert a preventive effect on scars. Evidence obtained from at least one properly designed randomized controlled trial. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .