Background Some micronutrients including selenium (Se) have immunoregulatory effects in the body. Our hypothesis was that decreased serum Se levels could be associated with some degree of immunodeficiency and increased chance of multiple cutaneous warts. Objective To measure serum Se levels in patients with multiple cutaneous warts and healthy participants to verify its inhibitory role in cutaneous warts. Patients and methods A case–control study was conducted on 136 participants: 68 cases with multiple cutaneous warts and 68 age-matched and sex-matched healthy controls. Collected data were age, sex, number, duration, and clinical type of the warts. Blood samples were taken from all participants for the evaluation of serum Se level. Se level was measured with atomic absorption method. Results Median of the Se level was significantly lower in patients with multiple warts compared with healthy controls (P