Background: Pharmaceutical services in Brazil provide access, supply, and rational use of drugs for all population and an effort has been made to improve the quality of these services. Biological drugs are high-cost drugs supplied in Brazil that can inhibit disease progression and improve the quality of life of psoriatic arthritis (PsA) patients. However, some patients did not achieve therapeutic goals. Objective: To evaluate the medication adherence and persistence of PsA patients treated with tumor necrosis factor inhibitors (anti-TNF) drugs and their associated factors. Methods: A prospective observational study was performed at a single-specialty pharmacy in Belo Horizonte, Brazil. Medication adherence, persistence, and clinical outcomes were evaluated at 12 months of follow-up. Medication persistence was historically compared to overall PsA patients treated in Brazil. Associated factors were identified through log-binomial regression. Results: One hundred ninety-seven PsA patients were included in the study, of whom 147 (74.6%) and 142 (72.1%) had medication adherence and persistence, respectively. Patients treated with infliximab presented the highest adherence (90.5%) and persistence rate (95.2%) in comparison to patients treated with other drugs, except for adalimumab versus infliximab for adherence outcome. All clinical measures significantly improved in patients with medication adherence and persistence. Medication persistence was higher for patients attended by specialty pharmacy than other PsA patients in Brazil. The associated factors to higher medication adherence were lower disease activity by BASDAI, being non-white race, and intravenous drug use. The associated factors to higher medication persistence were lower disease activity by Bath Ankylosing Spondylitis Activity Index (BASDAI), intravenous drug use, non-use of corticoids and non-steroidal anti-inflammatory drugs, and comorbidity. Conclusions: Patients with medication adherence and persistence had significant improvements in clinical measures, functionality, and quality of life. High medication adherence and persistence to biological therapy were observed and associated with lesser disease activity at baseline. Also, medication persistence to PsA patients attended in specialty pharmacy was higher than the overall PsA population in Brazil, which indicates the importance of pharmaceutical services to provide health care and promote the effectiveness and safety of biological therapies.