Background: The International Prognostic Index (IPI) scoring system is the most widely used prognostic tool for diffuse large B-cell lymphoma (DLBCL); however, it fails to consistently identify patients with poor outcomes. This retrospective study was undertaken to confirm the clinical value of a new prognostic score and compare it with the IPI. Methods: The aim of this single-center study was to confirm the clinical value of a new prognostic score and its association with various clinical features, disease progression, and death in 70 patients with DLBCL who had undergone at least 6 cycles of chemotherapy. Results: The IPI and the new prognostic index were both associated with 3-year mortality (p ≤ 0.032); however, only the new prognostic index was associated with 3-year progression (p ≤ 0.036). Multivariate analysis showed that the new prognostic index was associated with 3-year progression but not overall survival. The new prognostic score also distinguished 3-year progression-free survival and overall survival in the low- and low-intermediate-risk groups as well as in the low-intermediate- and high-intermediate-risk groups. Conclusions: The new prognostic score represents a comprehensive prognostic model superior to the IPI. Prospective studies are necessary to explore whether treatment strategies may be adjusted using this new prognostic score.