Introduction: Micronutrient deficiencies are common in Human Immunodeficiency Virus (HIV) infection. The long-term side effects of antiretroviral therapy (ART), specifically Azidothymine (AZT), include low serum levels of vitamin B12 and folate, which in turn, lead to megaloblastic anaemia and oral lesions. Methods: A crosssectional study was conducted to determine the associations between manifestation of oral lesions and serum vitamin B12 and folate levels in HIV-adult patients with or without receiving ART therapy. Oral lesions were determined based on the ECClearinghouse diagnostic criteria. Serum vitamin B12 and folate were assessed by electrochemiluminescence immunoassay (ECLIA). Sixty participants (48 males and 12 females) aged 20 to 51 years were recruited from a private hospital in Bandung, Indonesia. Results: Subnormal levels of serum vitamin B12 and folate were found in 16.6% and 6.7% HIV patients, respectively. Significantly lower serum levels of vitamin B12 and folate were shown in HIV patients receiving ART than those without ART. Oral lesions were found in all the participants with subnormal levels of serum vitamin B12 and folate. Presence of oral lesions was significantly associated with low levels of serum vitamin B12 in HIV patients with ART, but not with low folate levels. Conclusion: Low levels of serum vitamin B12 and folate were shown in HIV patients, indicating the need for early nutritional intervention to ensure optimal nutritional status and prevention of oral lesions in HIV patients.