Background: Blue light irradiation reduces the proliferation of keratinocytes and modulates T-cell immune response in vitro and has been shown to reduce the severity of psoriasis vulgaris (Pv) in two clinical trials. Objective: Evaluation of safety and efficacy of long-term UV-free blue light treatment at home for mild Pv. Methods: Forty-seven patients with mild Pv were randomized for receiving high-intensity blue light treatment (HI: 453 nm LED, 200 mW/cm2, n = 24) and low-intensity treatment (LI: 453 nm LED, 100 mW/cm2, n = 23) of one Pv plaque for 12 weeks. A contralateral control plaque remained untreated. Results: Patient compliance and satisfaction were high. The primary endpoint, change from baseline (CfB) of the Local Psoriasis Severity Index, revealed a significant improvement of the target compared to the control plaques (ΔCfB for the HI group: -0.92 ± 1.10, p = 0.0005; for the LI group: -0.74 ± 1.18, p = 0.0064). Conclusion: UV-free blue light home treatment is safe and improves Pv plaques.