BACKGROUND: Abnormal wound-healing after thyroidectomy with a resulting scar is a common dermatologic consultation. Despite many medical and surgical approaches, prevention of postoperative scars is challenging. OBJECTIVE: This study validated the efficacy and safety of low-level light therapy (LLLT) using an 830/590 nm light-emitting diode (LED)-based device for prevention of thyroidectomy scars. METHODS AND MATERIALS: Thirty-five patients with linear surgical suture lines after thyroidectomy were treated with 830/590 nm LED-LLLT. Daily application of 60 J/cm (11 minutes) for 1 week starting on postoperative day 1 was followed by treatment 3 times per week for 3 additional weeks. The control group (n = 15) remained untreated. Scar-prevention effects were evaluated 1 and 3 months after thyroidectomy with colorimetric evaluation using a tristimulus-color analyzer. The Vancouver Scar Scale (VSS) score, global assessment, and a subjective satisfaction score (range: 1-4) were also determined. RESULTS: Lightness (L*) and chrome values (a*) decreased significantly at the 3-month follow-up visit in the treatment group compared with those of controls. The average VSS and GAS scores were lower in the treatment group, whereas the subjective score was not significantly different. CONCLUSION: Light-emitting diode based LLLT treatment suppressed the formation of scars after thyroidectomy and could be safely used without noticeable adverse effects.