This study aimed to understand the influence of naïve T cells in cytokine-induced killer (CIK) cell immunotherapy. A total of 68 patients with advanced solid tumors received activated autologous CIK cells weekly. Objective responses (complete or partial responses, CR/PR) were observed in 11 patients (16.2%, 11/68), with five of 11 responses lasting more than 8 months, and in 16 patients with SD (23.5%, 16/68). The absolute number of CD4+ naïve T cells in patients who achieved CR/PR was higher in SD and PD patients (CR/PR vs SD vs PD= 90 vs 149 vs 226 cells/μL), as were the absolute number of CD8+ naïve T cells (CR/PR vs SD vs PD= 47 vs 60 vs 103 cells/μL). Patients with high absolute numbers of naïve T cells ({greater than or equal to}298 cells/μL in naïve CD4+ and {greater than or equal to}156 cells/μL in naïve CD8+ cells) had a better response to ACT (PFS=8 months vs 5 months). In this study, we found that Patients with a high absolute number of naïve T cells in circulating blood had a better response to ACT, which showed the potential of naïve T cells as a biomarker for the response to ACT.