The human immunodeficiency virus (HIV) is the virus that attacks the body's functional immune system, targets the CD4 T-cells, progressing to acquired immunodeficiency syndrome (AIDS), and leading to death when improperly treated. Since, presently, HIV/AIDS has no known cure, adherence to antiretroviral therapy (ART) is crucial to minimize viral replication and improve disease outcomes. However, many factors affect medication adherence among patients, sometimes leading to treatment failure and often resulting in complications that could lead to death. This study assessed medication adherence and factors affecting medication adherence to ART in HIV/AIDS patients in Belize. The research design was a cross-sectional study conducted in Belize at public hospitals and clinics across the country at locations where ART medicines are provided to patients. The participants were purposively selected from the nine testing and ART provision sites, being 18 years and older, and actively receiving ART. The visual analog scale (VAS) survey tool was utilized to obtain data on factors influencing treatment adherence. One hundred forty-seven participants, 18 years and older, receiving ART responded to the survey. The collected data were analyzed using SPSS. The study results indicated that 72.8% of the participants reported optimal adherence to the VAS assessment and 85.7% to the subjective assessment, thus reporting optimal or excellent adherence between 90% and 100%. Fear of disclosing HIV status due to discrimination and stigma was the main reason reported by participants, indicating the existence of stigma toward PLWHA among the Belizean population. The majority of the participants in this study reported optimal adherence to ART in Belize. The provision of more support, guidance, and counseling to patients living with HIV/AIDS is recommended. Public awareness to discourage and minimize discrimination and stigma toward HIV/AIDS patients was also recommended.