The aim of the study was to assess the prevalence of moderate to severe psoriasis (MS-P) in patients with psoriatic arthritis (PsA) and the relationship between MS-P and other variables related to arthritis. One hundred sixty-six consecutive patients with PsA periodically monitored at a university hospital's PsA unit in northeastern Spain were included in the study. Patients with psoriasis were classified as having MS-P when systemic treatment for skin was required. Clinical criteria for treatment indication was BSA >10 and/or PASI >14 and/or psoriasis affecting a very sensitive area of the body. Demographic and clinical data related to arthritis were assessed, including PsA pattern, age of onset of psoriasis and arthritis, disease activity index, and treatment required over the course of the disease. Moderate-severe psoriasis were more prevalent in women (p = 0.027). One hundred nine patients (65.7%) had psoriatic nail disease, and MS-P was more frequent in these patients (40 (77%) vs. 69 (61%), p = 0.028). Patients with spondyloarthropathy were significantly associated with MS-P (7 (16%) vs. 3 (3%), p = 0.014). No statistical association was observed between severe psoriasis and the age of onset of psoriasis or arthritis, involvement of distal interphalangeal joints, laboratory findings (HLA B27, RF), functional class, or disease activity indices. We report a high prevalence of severe psoriasis among patients with psoriatic arthritis, higher in women and patients with psoriatic nail disease and axial spondyloarthropathy.