BACKGROUND: Vulvar lichen planus (VLP) is a chronic vulvar dermatosis that is difficult to treat and can severely impair quality of life in the absence of adequate treatment. There is a lack of high-quality evidence to direct therapy for VLP. This randomised controlled trial will be the first double-blinded study comparing systemic treatments in VLP and aims to investigate the safety and efficacy of deucravacitinib compared to methotrexate, in patients with VLP who have failed treatment with potent topical corticosteroids. METHODS: A total of 116 women aged ≥ 18 years with moderate to severe VLP (Genital Erosive Lichen Planus (GELP) score ≥ 5) will be recruited. All participants will initially be treated with Diprosone® OV daily, and their outcome will be assessed using the GELP score. At 8 weeks' follow-up, responders (GELP < 5) will be continued on Diprosone® OV. Non-responders (GELP ≥ 5) will be randomised 1:1 in a blinded fashion to receive (i) methotrexate 10 mg weekly + placebo tablet twice daily + folic acid 5 mg weekly or (ii) deucravacitinib 6 mg twice daily + placebo tablet weekly + folic acid 5 mg weekly. The primary endpoint is the difference in the mean change of GELP scores from baseline to week 32 between deucravacitinib and methotrexate groups. DISCUSSION: High-quality evidence guiding the management of women with VLP is lacking. Once completed, this will be the first double-blinded RCT to compare systemic treatments in VLP. The results of this study will provide valuable, high-quality data to guide second-line therapy options for VLP that is recalcitrant to potent topical corticosteroids. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12623000682640. Registered on 26 June 2023.