In our previous study on nm23-H1 expression with diffuse large B-cell lymphoma (DLBCL), we found that patients with positive nm23-H1 had significantly poorer prognosis than patients with negative nm23-H1. We examined whether nm23-H1 is a prognostic factor of DLBCL in the rituximab era. The subjects were 101 DLBCL patients who underwent R-CyclOBEAP (rituximab, cyclophosphamide, vincristine, bleomycin, etoposide, doxorubicin, and prednisolone) therapy and in whom markers could be analyzed. We evaluated CD5, CD10, BCL2, BCL6, MUM1, and nm23-H1 expression by immunohistochemistry. Ninety-four DLBCL patients who underwent CyclOBEAP therapy were assumed as historical controls. Among DLBCL patients who underwent CyclOBEAP therapy, BCL2 positivity, MUM1 positivity, non-germinal center B-cell (non-GCB), and nm23-H1 positivity were associated with significantly shorter overall survival (OS) and progression-free survival (PFS). On the other hand, among DLBCL patients who underwent R-CyclOBEAP therapy, the 5-year OS rates of the nm23-H1-positive DLBCL (n = 32) and nm23-H1-negative DLBCL groups (n = 69) were 65% and 97%, respectively (p = 0.001), with 5-year PFS rates of 51% and 89%, respectively (p = 0.001). In the rituximab era, BCL2, MUM1, and non-GCB were not prognostic factors. We demonstrated that among patients with DLBCL who underwent R-CyclOBEAP therapy, patients with nm23-H1 expression had a significantly poorer prognosis than patients without nm23-H1 expression. These results suggest an important role for nm23-H1 in malignant progression and a potential therapeutic target for DLBCL.