Cytomegalovirus (CMV) is a well-established cause of morbidity and mortality in pediatric recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT). CD8⁺ T-cells are important for controlling CMV infection. We conducted a prospective pilot study to investigate the clinical utility of measuring the CMV-specific T-cell immune response using the QuantiFERON-CMV assay (QF-CMV) in pediatric allo-HSCT recipients. Overall, 16 of 25 (64%) patients developed CMV infection. QF-CMV was evaluated in these 16 patients during the early and late phases of the first CMV infection post allo-HSCT. Whereas the initial QF-CMV results during the early phase of CMV infection did not correlate with the course of the corresponding infection, the QF-CMV results post resolution of the first CMV infection correlated with the recurrence of CMV infection until 12 months post allo-HSCT; no recurrent infections occurred in the four QF-CMV-positive patients, while recurrent infections manifested in five of eight QF-CMV-negative (62.5%) and all three QF-CMV-indeterminate patients (P=0.019). In spite of the small number of patients examined, this study supports the potential application of monitoring CMV-specific T-cell immunity using the QF-CMV assay to predict the recurrence of CMV infection in pediatric allo-HSCT recipients.