Background Health literacy (HL) is the ability to access, understand and utilize information and health services. People living with HIV (PLWH) with high HL have higher adherence to antiretroviral therapy (ART) and better long-term health outcomes. Since HL has a crucial impact on health outcomes, we conducted the first study in Türkiye to identify factors associated with HL in PLWH. Methods A questionnaire containing demographic data and the HÜ-SOY scale to measure HL levels was completed by 244 PLWH who agreed to participate in our study. The achieved sample size was sufficient to detect small-to-moderate effect sizes, as supported by power and sensitivity analyses. Regarding adherence to ART, the individuals were asked whether they had not taken ART for two consecutive days or for a total of 30 days in the last year. Results HL levels were lower in patients with low ART adherence (p = 0.007). A higher level of HL was observed in individuals whose income levels exceeded their expenses and in those with higher education levels (p < 0.001). Those who did not want to specify their sexual orientation had lower levels of HL (p = 0.001). The HL level was higher in the group with higher CD4 count but not statistically significant. In multivariable linear regression analysis, higher educational level and sexual orientation remained independently associated with HL levels. Conclusions HL levels should be assessed before starting ART, and PLWH with low HL should be considered at high risk for treatment nonadherence. On the other hand, for individuals who do not want to disclose their sexual orientation, interventions that increase their HL levels may be beneficial for them to express themselves freely.