Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma in Egypt and worldwide. Gene expression profiling classifies DLBCL into: germinal center B cell-like (GCB) and non germinal center B cell-like (non-GCB) DLBCL. Hans' algorithm has high concordance with gene expression profiling results. Regulatory T cells (Tregs) represent important modulators for the interaction between lymphoma cells and host microenvironment. FOXP3 is a popular single marker for Tregs. There is little information about the possible role of Tregs in high-grade lymphoma such as DLBCL. This study aims to assess the prognostic impact of FOXP3+ Tregs in DLBCL. The study was carried out on 70 archival cases (61 de novo DLBCL and 9 reactive follicular hyperplasia cases). DLBCL cases were classified into GCB and non-GCB groups using Hans' algorithm. All studied cases are subjected to FOXP3 immunostaining. Density of FOXP3+ Tregs was higher in reactive cases compared with DLBCL (P=0.000). In DLBCL cases, FOXP3 expression was associated with free spleen (P=0.02), early stage (P=0.05), centroblastic variant (P=0.003), and absence of necrosis (P=0.05). In germinal cases, density of FOXP3 was significantly higher in cases with good PS (P=0.02), very good and good revised international prognostic index (P=0.002), and low-risk age-adjusted international prognostic index >60 (P=0.01). Non germinal DLBCL cases with negative FOXP3 were significantly associated with splenic involvement (P=0.005). DLBCL cases with high FOXP3 have longer survival (P=0.03). T cells in the background of DLBCL may play a role in modulation of tumor progression. Their presence is associated with favorable prognostic parameters in DLBCL.