Background: Treatment of cellulite using a 1440-nm YAG wavelength laser with side-firing fiber has proven safe and effective, lasting at least 6 months. Objectives: The authors evaluate the safety and efficacy of a single, subdermal procedure to treat the underlying structure of cellulite for at least 1 year. Methods: Fifty-seven patients underwent a 3-step cellulite treatment with a 1440-nm Nd:YAG laser with a side-firing fiber and temperature-sensing cannula. Efficacy was measured by the blinded evaluators to distinguish baseline photos from those taken at 12 months posttreatment, with results on a 5-point, 2-category ordinal photonumeric scale when comparing baseline photos to 12 months posttreatment. Subject and physician satisfaction was assessed based on completion of a satisfaction survey. Adverse events (AE) were recorded throughout the study. Twelve month data were analyzed and compared to 6 month data. Results: Evaluators chose baseline photographs 97% on average from 6 (-1, +2) months and 91% from the 12 (-3, +2) months posttreatment photographs. At 6 (-1, +2) months, the average improvement score was 1.7 for dimples and 1.1 for contour irregularities. At 12 (-3, +2) months, the average improvement score was 1.4 for dimples and 1.0 for contour irregularities. The average satisfaction score for the physician was 5.6 and the patient was 5.3 on a 6-point scale. Conclusions: A single, 3-step, minimally invasive laser treatment using a 1440-nm Nd:YAG laser, side-firing fiber, and temperature-sensing cannula to treat the underlying structure of cellulite proved to be safe and maintained effectiveness at least 1 year post treatment.