Objective: The findings on chronic myeloid leukemia (CML) patients suggest that clonal tumoral cells tend to have additional mutations besides the formation of the BCR-ABL fusion gene. Previous studies have demonstrated abnormal activation-induced cytidine deaminase (AID) expression in various types of cancer, showing AID transcript levels to be elevated in the CML blast phase. The study aimed to investigate the AID gene expression levels in CML and to investigate the etiopathogenic role of AID, which is not yet fully understood. Materials and Methods: This study analyzed the AID transcript levels of 80 CML patients and 50 controls using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). Results: The study found the AID transcript levels to be significantly elevated (p < 0.001) in the CML patients compared to the control group, with no significance in AID transcript levels with regard to the patients’ age, gender, clinical characteristics, or laboratory findings. No correlation was found between the AID and BCR-ABL transcript levels, while a positive correlation was present between AID transcript levels and presence of polymorphonuclear leukocytes (PMNL; r = 0.320, p = 0.021). No significant relationship occurred in AID transcription levels with the tyrosine-kinase-inhibitor (TKI) resistant mutation profile or cytogenetic response during TKI therapy. Conclusion: This study found AID expression levels to be significantly elevated in CML patients and AID to be able to contribute to the etiopathogenesis of CML