The coexistence of psoriasis with systemic lupus erythematosus (SLE) has been reported in limited case series, raising hypotheses about shared pathogenetic mechanisms. Nevertheless, important differences regarding treatment do exist. The aim of the present study was to determine the prevalence and characteristics of psoriasis in a defined cohort of lupus patients. Patients with psoriasis were retrieved from the University of Toronto Lupus Clinic from its inception in 1970 up to 2015. Charts were hand-searched to collect information concerning demographic, clinical, and therapeutic variables. Patients were matched with non-psoriasis lupus patients to identify the impact of supervening psoriasis on lupus activity, damage accrual, and venous thromboembolic (VTEs) and cardiovascular events (CVEs). Psoriasis was diagnosed in 63 patients (49 females, 14 males) for a prevalence of 3.46% (63/1823). The male-to-female ratio was significantly higher in non-psoriasis patients (0.286 vs. 0.138, p = 0.017). Plaque psoriasis was the most prominent type (55/63, 87.3%) whereas three patients had pustular disease; one had psoriatic arthritis. Nine patients (14.3%) were administered systemic treatment with methotrexate (n = 5), azathioprine (n = 1), ustekinumab (n = 3), and etanercept (n = 1). Psoriasis was definitely deteriorated by hydroxychloroquine in one patient. There was no significant impact of psoriasis on disease activity, damage accrual, VTEs, and CVEs. The prevalence of psoriasis was twice as high as that of the general Canadian population in this lupus cohort. Plaque psoriasis was the most prominent subtype, and topical treatment was adequate in the majority of patients. Supervening psoriasis had no significant impact on lupus activity and damage accrual.