Combined axitinib/pembrolizumab is approved for advanced renal cell carcinoma (aRCC). This exploratory analysis examined associations between angiogenic and immune-related biomarkers and outcomes following axitinib/pembrolizumab treatment. Prospectively defined retrospective correlative exploratory analyses tested biospecimens from 52 treatment-naïve patients receiving axitinib and pembrolizumab (starting doses 5 mg twice daily and 2 mg/kg respectively, every 3 weeks). Tumor tissue, serum, and whole blood samples were collected at baseline, at cycle 2 day 1 (C2D1), and end of treatment (EOT) for blood-based samples. Clinical outcomes were objective response rate (ORR) and progression-free survival (PFS). Higher baseline tumor levels of CD8 showed a trend toward longer PFS (HR 0.4; = 0.091). Higher baseline serum levels of CXCL10 ( = 0.0197) and CEACAM1 ( = 0.085) showed a trend toward better ORR and longer PFS, respectively. Patients for whom IL6 was not detected at baseline had longer PFS versus patients for whom it was detected (HR 0.4; = 0.028). At C2D1 and/or EOT, mainly immune-related biomarkers showed any association with better outcomes. The genes ( = 0.084), ( = 0.064), and ( = 0.073) showed trending associations with ORR, and ( = 0.0145), ( = 0.0726), ( = 0.0666), ( ; = 0.0267), and ( = 0.0287) with PFS. With combined axitinib/pembrolizumab treatment in patients with aRCC, mostly immune-related biomarkers are associated with better treatment outcomes. This exploratory analysis has identified some candidate biomarkers to consider in future prospective testing.