Cytomegalovirus (CMV) is known to alter circulating effector memory or re-expressing CD45RA+(TemRA) T-cell numbers, but whether Epstein–Barr virus (EBV) does the same or this is amplified during a CMV and EBV co-infection is unclear. Immune cell numbers in blood of children and young, middle-aged, and senior adults (n= 336) were determined with flow cytometry, and additional multivariate linear regression, intra-group correlation, and cluster analyses were performed. Compared to non-infected controls, CMV-seropositive individuals from all age groups had more immune cell variance, and CMV+EBV−senior adults had more late-differentiated CD4+and CD8+TemRA and CD4+effector memory T-cells. EBV-seropositive children and young adults had a more equal immune cell composition than non-infected controls, and CMV−EBV+senior adults had more intermediate/late-differentiated CD4+TemRA and effector memory T-cells than non-infected controls. CMV and EBV co-infected young and middle-aged adults with an elevated BMI and anti-CMV antibody levels had a similar immune cell composition as senior adults, and CMV+EBV+middle-aged adults had more late-differentiated CD8+TemRA, effector memory, and HLA-DR+CD38−T-cells than CMV+EBV−controls. This study identified changes in T-cell numbers in CMV- or EBV-seropositive individuals and that some CMV and EBV co-infected young and middle-aged adults had an aging-related T-cell phenotype.