Early relapse is a parameter that affects clinical outcomes in relapsed diffuse large B cell lymphoma (DLBCL). The prognostic value of lymphopenia following the completion of first-line therapy and the relationship between lymphopenia and early relapse are unknown. Therefore, we studied the role of absolute lymphocyte count (ALC) on early relapse. We retrospectively analyzed de novo DLBCL patients who were treated with rituximab-containing treatment between 2003 and 2010. The median age at the time of diagnosis of 59 DLBCL patients was 71 years. We identified no association between ALC at diagnosis and ALC following the completion of first-line therapy. Among all patients analyzed, 13 (22%) patients were confirmed to exhibit early relapse. Low ALC following the completion of first-line therapy was significantly associated with early relapse by univariate analysis [hazard ratio (HR) = 4.05; 95% confidence interval (CI), 1.11-14.73; P = 0.02] and multivariate analysis (HR = 4.66; 95% CI, 1.24-17.48; P = 0.023). The low ALC group tended to have worse outcomes than the high ALC group with lower rates of progression-free survival (66% and 74%, respectively; P = 0.13) and overall survival (74% and 86%, respectively; P = 0.09), but these differences did not reach statistically. Lymphopenia following the completion of first-line therapy can be used as a marker to predict early relapse.