Introduction: HIV status disclosure to children remains complex and constrained by child-, caregiver-, and health-system-level factors. Aim: To assess factors associated with caregiver-reported HIV status disclosure among children and adolescents receiving antiretroviral therapy (ART) and explore associations between disclosure status and selected treatment-related indicators in rural Eastern Cape province. Methods: A cross-sectional study of 87 caregiver–child dyads was conducted across five public ART clinics. Data were collected using caregiver questionnaires and abstraction from ART records. Bivariate associations were assessed using Pearson’s chi-square or Fisher’s exact tests, and multivariable binary logistic regression was performed to identify caregiver-related factors independently associated with HIV status non-disclosure. Results: Overall, 44.8% (n = 39) of children and adolescents had been informed of their HIV status. Status disclosure was associated with older age and legal guardian caregiving (p < 0.001, respectively). Participants who had been disclosed to had higher rates of viral suppression (74.4% vs. 29.2%), optimal ART adherence (87.2% vs. 45.8%), and independent medication administration (82.1% vs. 33.3%) (all p < 0.001). In multivariable analysis, caregiver readiness to discuss HIV was associated with lower odds of non-disclosure (AOR = 0.037; 95% CI: 0.004–0.381), whereas the perceived need for additional disclosure training and counselling (AOR = 15.97; 95% CI: 3.05–83.53) and biological-parent caregiving (AOR = 11.92; 95% CI: 2.16–65.67) were associated with higher odds of non-disclosure. Conclusion: HIV disclosure was associated with developmental, caregiving, and treatment-related factors. Strengthening structured caregiver preparation and disclosure support within routine paediatric HIV services may improve implementation, although longitudinal studies are needed to clarify temporal relationships and causal pathways.