Psoriasis has a devastating psychological impact on patients' quality of life. However, the relationship between suicidality and psoriasis remains unclear. This study analysed and compared the risk of suicidality (suicidal ideation, suicide attempt and completed suicide) between patients with psoriasis and the general population. This nationwide, population-based, retrospective, cohort study analysed the Korean National Health Insurance Service claim data from 2005 to 2018. The study included 348,439 patients with psoriasis aged over 18 years and with age- and sex-matched controls. The risk of suicidality was higher in the psoriasis group than in the control group [adjusted hazard ratio (aHR) 1.21; 95% confidence interval (CI), 1.18-1.24]. The aHR of suicidality was higher in the psoriatic arthritis group (aHR, 1.46; 95% CI, 1.39-1.54) than in the psoriasis-alone group (aHR, 1.17; 95% CI, 1.13-1.20). However, the severity of psoriasis and suicidality showed no correlation (mild psoriasis group: aHR, 1.22; 95% CI, 1.18-1.25; moderate-to-severe psoriasis group: aHR, 1.16; 95% CI, 1.10-1.23). Patients with psoriasis have an increased risk of suicidality. In particular, the presence of arthritis in patients had a more significant effect on the risk of suicidality.