Resistance to immune checkpoint inhibitors (ICI) in cancer patients is not fully understood, and predictive biomarkers are lacking. MELANFα (NCT03348891) is an open-label, prospective, multicenter cohort of 60 patients with advanced melanoma receiving ICI (bitherapy: ipilimumab + nivolumab; monotherapy: pembrolizumab or nivolumab). The primary objective was to evaluate whether changes in plasma TNF between baseline (W0) and week 12 (W12) identified patients with non-progressive disease at W12. Secondary and exploratory objectives were to assess the association between plasma TNF, tumor response, and changes in circulating T cells. Plasma TNF increased along therapy, but its W12/W0 fold change was not associated with non-progressive disease at W12. However, plasma TNF levels at W12 were significantly higher in non-responders than in responders across therapies (p = .0129). The remodeling of circulating T cell subpopulations was mostly triggered by bitherapy. Increased proportions of circulating central memory and effector memory CD8 T cells after bitherapy were positively and negatively associated with response to treatment, respectively. In this cohort, circulating T cells from responders and non-responders also displayed distinct molecular characteristics. Indeed, responders showed an increased proportion of CD8 T cells with low enrichment of TNF-related pathways and high cytotoxic potential, while non-responders displayed increased proportions of circulating CD8 EM T cells enriched for TNF-related pathways and directed toward cytokine expression. In conclusion, our study shows that elevated plasma TNF and enriched TNF pathways in T cells are associated with poorer clinical outcomes, reinforcing the notion that TNF may dampen ICI efficacy.