<p>Serum albumin and uric acid (UA), both recognized for their antioxidant properties, have been linked to Parkinson’s disease (PD) progression. However, their associations with neurocognitive performance and physical fitness in early-stage PD remain unclear. To examine relationships between albumin and UA with cognitive performance, neurophysiological indices, and physical function in early-stage PD. Forty-eight individuals with early-stage PD were stratified into high and low groups based on median serum albumin and UA levels. Supplementary regression analyses examined dose-response associations. Neurocognitive performance was assessed via a working memory task with event-related potential (ERP) recordings. Physical fitness measures included cardiorespiratory fitness, muscle strength, and the 8-foot Timed Up-and-Go (TUG) test. Group comparisons used repeated-measures analysis of variance (ANOVA) and nonparametric tests. Higher albumin and UA levels were associated with lower motor severity; higher UA also linked to better global cognition. Both high-level groups showed faster reaction times. ERP analysis revealed higher UA associated with more negative N2 and smaller P3 amplitudes, suggesting efficient conflict monitoring and attentional processing. Both groups performed better on TUG, while only high albumin showed superior cardiorespiratory fitness. Regression models revealed a consistent linear protective trend for UA, whereas albumin exhibited an inverted U-shaped relationship with global cognition. Higher serum albumin and UA levels within the normal range are associated with superior neural efficiency and functional mobility in early-stage PD. These biomarkers may reflect systemic metabolic reserve associated with motor and cognitive function in early-stage PD.</p>