Background: There are significant number of patients who are on highly active antiretroviral therapy (HAART) not virally suppressed, which is a huge clinical challenge. Social support as a non-pharmacological factor, which may influence the viral suppression, is less studied and has equivocal results. The aim of this study was to investigate the association between social support and viral load (VL) in adults on HAART.Methods: This was an analytical cross-sectional study. Using a structured questionnaire, 380 adults (≥ 18 years) on HAART for ≥ 6 months were recruited between November 2018 and February 2019 from Witbank hospital and surrounding clinics. Multivariable logistic regression was carried out.Results: The mean age of the participants was 40.5 years (s.d. = 10.3). The majority were females (73%), at least high school educated (84%), unemployed (57%), single (63%) and did not have comorbidity (80%). The vast majority had moderate to high adherence (84%) and moderate to good perceived social support (94%). The viral suppression rate was 87%. Both adherence (p 0.001) and social support (p = 0.017) were significantly associated with VL. However, only adherence was predictive of viral suppression in multivariable analysis. Compared to poorly adherent, moderately (OR = 2.8; 95% CI = 1.32–5.98) and highly (OR = 5.3; 95% CI = 2.41–11.81) adherent participants were more likely to have suppressed VL.Conclusion: Viral suppression rate was high. Self-reported adherence to HAART was highly predictive of viral suppression, which highlights the importance of assessing and addressing adherence issues at every contact with patients taking HAART. Good social support did not predict viral suppression.