To evaluate the association of serum biomarkers with baseline psoriatic arthritis (PsA) disease activity, pharmacodynamic effects of deucravacitinib on biomarker levels, and relationship between biomarkers and clinical responses to deucravacitinib. The phase 2 trial (NCT03881059) randomized 203 patients with PsA 1:1:1 to placebo, deucravacitinib 6 mg once daily (QD), or deucravacitinib 12 mg QD. Serum biomarkers associated with the IL-23 pathway (IL-17A, BD-2, and IL-19), Type I interferon pathway, inflammation, and collagen matrix turnover were measured by immunoassay. Clinical responses (≥75% improvement from baseline in Psoriasis Area and Severity Index [PASI 75] and ≥20% improvement from baseline in American College of Rheumatology [ACR 20] criteria responses) were measured at week 16. Hematologic variables were also assessed. IL-17A, BD-2, and IL-19 had a modest association with PASI scores (r=0.4, r=0.56, and r=0.5, respectively) at baseline. In deucravacitinib groups, IL-17A, BD-2, IL-19, CXCL-9, CXCL-10, CRP, MMP3, and C4M levels were significantly reduced at week 16 versus baseline (P<0.01); higher levels of IL-23 pathway-associated biomarkers predicted higher PASI 75 and ACR 20 response rates in deucravacitinib-treated patients. Significantly higher PASI 75 response rates were seen in patients with high baseline IL-17A (OR: 15.76) and BD-2 (OR: 15.41) versus low. Changes in hematologic variables that are characteristic of JAK inhibition were not observed with deucravacitinib. Deucravacitinib significantly impacted biomarkers associated with TYK2 signaling pathways of key inflammatory cytokines, including IL-23 and Type I IFN, and those related to collagen matrix turnover. These biomarkers may predict treatment responses to deucravacitinib.