Cord blood has gradually become an important source for hematopoietic stem cell transplantation (HSCT) in the human, particularly in pediatric patients. Adoptive cellular immunotherapy of patients with hematologic malignancies after umbilical cord blood transplant is crucial. Cytokine‑induced killer (CIK) cells derived from cord blood are a new type of antitumor immune effector cells in tumor prevention and treatment and have increasingly attracted the attention of researchers. On the other hand, it has been suggested that preterm infant cord blood retains an early differentiation phenotype suitable for immunotherapy. Therefore, we determined the phenotypic and functional characterization of CIK cells derived from preterm infant cord blood (PCB-CIK) compared with CIK cells from term infant cord blood (TCB-CIK). Twenty cord blood samples were collected and classified into two groups based on gestational age. Cord blood mononuclear cells (CBMCs) were isolated, cultured and induced to CIK cells in vitro. We used flow cytometry to detect cell surface markers, FlowJo software to analyze the proliferation profile and intracellular staining to test the secretion of cytokines. Finally, we evaluated the antitumor activity of CIK cells against K562 in vitro. Compared with TCB-CIK, PCB-CIK cells demonstrated faster proliferation and higher expression of activated cell surface markers. The secretion of IL-10 was lower in PCB-CIK cells while the expression of perforin and CD107a had no significant difference between the two cell groups. PCB-CIK cells exhibited a high proliferation rate while the cytotoxic activity had no difference between the PCB-CIK and TCB-CIK cells. Hence preterm infant cord blood may be a potential source for immunotherapy.