Objective: To investigate the effect of biologic treatments for psoriasis on the incidence of psoriatic arthritis (PsA). Methods: This retrospective cohort study was conducted using electronic medical records from a large health maintenance organization. Patients who received biologic treatment for psoriasis and were not diagnosed as having PsA before or at the time of biologic treatment initiation were included. Control psoriasis patients who did not receive biologic treatment were matched by age at time of diagnosis, sex, time from psoriasis diagnosis until treatment initiation, maximum body mass index, and smoking status. The groups were different in most characteristics. Therefore, propensity score matching was implemented. Log rank test and multivariable Cox proportional hazards regression were used to compare the groups. Results: Overall, 1,326 patients were included, of whom 663 had received biologic treatment and 663 had not. The Kaplan-Meier curve for the propensity score–matched groups reflected a statistically significant increased risk for PsA among the control group compared to the biologic treatment group. The results of the multivariable Cox regression showed that the control group had a significantly higher risk for PsA compared to the biologic treatment group within 10 years of follow-up (adjusted hazard ratio 1.39 [95% confidence interval 1.03–1.87]). Conclusion: Our findings show a statistically and clinically significant decreased risk for developing PsA among patients with psoriasis who receive biologic treatments. The results suggest that biologic medications should be considered for patients who present with significant risk factors for PsA at an earlier stage of treatment.