Background: A knee arthroplasty results in a long vertical scar on the knee and has a high risk for the development of hypertrophic or keloid scarring. The purpose of this study is to determine the efficacy and safety of the use of a 595 nm pulsed-dye-laser (PDL) for this type of scar. Methods: This randomized, controlled study was conducted in 40 patients (41 scars) with postoperative knee arthroplasties. Each scar was divided at the midline into two sections and randomized into a laser treated half and a controlled half. The treated half has received three treatments with a 595 nm PDL (10 mm spot size, 0.45 ms, 6 J/cm²). The scar appearances had been evaluated at 6 months using the Vancouver scar scale (VSS). Results: At 6 months postoperative, the laser treated sections had demonstrated significantly better scores in the overall parameters of the VSS. Furthermore, as for the individual parameters, there were significant differences between the treatment sections and control sections with the exception of pigmentation. There were no serious complications. Conclusion: The 595 nm PDL is an effective and safe therapeutic option for the treatment of surgical scars following a knee arthroplasty.