Interferon-beta has been suggested as a trigger of psoriasis, yet a systematic investigation is lacking. This study aimed to assess the risk of developing psoriasis following interferon-beta treatment, utilizing a pharmaco-epidemiological approach to investigate the role of interferon-beta in psoriasis pathogenesis. We included all treatment-naïve patients with multiple sclerosis (MS) in Denmark who initiated interferon-beta treatment for MS from January 1996 to June 2023. These patients were compared to a control cohort of patients with MS treated with other disease-modifying drugs. We compared the incidence rates of psoriasis before and during the treatment. Data for this study were extracted from the Danish MS Registry and integrated with information from other national Danish health registries. Among 7174 patients treated with interferon-beta, the incidence rate of psoriasis post-treatment initiation was slightly higher (2.01 per 1000 person-years) compared to the rate prior to treatment (1.67 per 1000 person-years). This increase did not achieve statistical significance (P = 0.53), with an incidence rate ratio (IRR) of 1.20 (95% confidence interval [CI] 0.68–2.13). The control cohort showed an increase in psoriasis incidence post-treatment initiation (3.12 per 1000 person-years) compared to prior (1.11 per 1000 person-years), with an IRR of 2.80 (95% CI 1.36–4.77, P = 0.0038). This registry-based self-controlled study does not support the theory that interferon-beta acts as a trigger for psoriasis development.