Human leukocyte antigen-G (HLA-G) is a nonclassical HLA class I molecule that exerts an immunosuppressive function. A 14-base pair (bp) sequence insertion/deletion (INS/DEL) polymorphism in the exon 8 at the 3′ untranslated region (UTR) modifies mRNA stability and protein production and has been shown to concur with efficacy of pharmacological treatments in immune-mediated conditions. The aim of this study was to assess for the first time the correlation between HLA-G 14-bp INS/DEL polymorphism with the response to systemic therapy in psoriatic patients. We retrospectively analyzed the HLA-G 14-bp INS/DEL polymorphism of HLA-G gene in patients with moderate to severe plaque psoriasis: 21 treated with acitretin, 16 with cyclosporine, 11 with anti-TNF-α. Patients who reached PASI 75 at weeks 10–16 were considered responders. Among patients treated with acitretin, we observed a significantly increased frequency of the HLA-G DEL allele and of the DEL/DEL genotype in responder patients when compared with nonresponders. An association between HLA-G genotype and response to cyclosporine and biologics was not found. The significant association between HLA-G 14-bp DEL allele and 14-bp DEL/DEL genotype and acitretin clinical outcome may suggest an advantage of this allele and propose this HLA-G polymorphism as a potential marker of response to acitretin in psoriatic patients.