Objective: Drug-resistant isolates of human cytomegalovirus (HCMV) have led to the development of new anti-HCMV drugs. Maribavir (MBV) is a novel inhibitor of the HCMV viral kinase. Resistance to MBV is mapped to gene UL27, a viral nuclear protein. In this study, we investigated UL27 polymorphisms in MBV-naive HIV-positive and HCMV congenitally infected clinical samples. Methods: DNA was extracted from 20 CMV-positive HIV (9/20) and congenitally infected (11/20) patients and used for UL27 polymerase chain reaction amplification. Sanger sequencing and multiple sequence alignment of products was performed. Results: K90 was the most prevalent polymorphism in both HIV-positive and congenitally infected patients. Polymorphisms Q54, D123, and R107 (10%) were seen in more than one sample. There were significantly more polymorphisms in the HIV-positive samples (p = 0.038). Conclusion: HCMV pUL27 is highly variable in adult immunocompromised HIV-positive patients.