Psoriasis (PsO) is a chronic inflammatory skin disease that affects 2-3% of the adult population worldwide. Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy that occurs in 20-30% of PsO patients. PsA is characterized by a heterogeneous clinical phenotype that makes diagnosis and treatment challenging. Currently, diagnosis is predominantly based on clinical findings, highlighting the need for reliable biomarkers to improve diagnostic precision, refine prognostic evaluations, and guide personalized therapeutic strategies. Recent advances in proteomic methodologies have provided novel insights into the pathophysiology and diagnosis of PsA. This review synthesizes the current evidence on protein biomarkers associated with PsA, focusing on nontargeted chromatographic proteomic approaches. These methodologies can enable comprehensive analysis of diverse biological specimens, facilitating the identification of candidate proteins that could be incorporated into targeted enzymatic and immunological panels for routine clinical practice in the future. Our review identified 72 isolated proteins and one protein combination with potential diagnostic utility for PsA, with particular emphasis on biomarkers such as NAD-dependent sirtuin-2 deacetylase (SIRT2), stress-induced phosphoprotein 1 (STIP1), and thymosin beta 4 (TMSB4X). Despite the growing interest in proteomic approaches for PsA, additional investigations with larger, well-stratified patient cohorts are necessary to validate these findings, establish robust diagnostic biomarkers, and facilitate their clinical implementation.