Human immunodeficiency virus remains a global public health problem. Despite efforts to determine the prevalence of non-adherence to ART and its predictors in Ethiopia, various primary studies presented inconsistent findings. Therefore, this review aimed to determine the pooled prevalence of non-adherence to ART and identify its predictors. We have searched PubMed, Google Scholar and Web of Science databases extensively for all available studies. A weighted inverse-variance random-effects model was used to compute the overall non-adherence to ART. The pooled prevalence of non-adherence to ART was 20.68% (95% CI: 17.74, 23.61); I2 = 98.40%; p < 0.001). Educational level of primary school and lower [AOR = 3.5, 95%CI: 1.7, 7.4], taking co-medications [AOR = 0.45, 95%CI: 0.35, 0.59], not using memory aids [AOR = 0.30, 95%CI: 0.13, 0.71], depression [AOR = 2.0, 95%CI: 1.05, 3.79], comorbidity [AOR = 2.12, 95%CI: 1.16, 3.09), under-nutrition [AOR = 2.02, 95%CI: 1.20, 3.43], not believing on ART can control HIV [AOR = 2.31, 95%CI: 1.92, 2.77], lack of access to health facilities [AOR = 3.86, 95%CI: 1.10, 13.51] and taking ART pills uncomfortably while others looking [AOR = 5.21, 95%CI: 2.56, 10.53] were significantly associated with non-adherence to anti-retroviral therapy. The overall pooled prevalence of non-adherence to ART was considerably high in Ethiopia. Educational status, taking co-medications, not using memory aids, depression, comorbidity, under nutrition, not believing on anti-retroviral therapy controls HIV, lack of access to health facilities and taking ART pills uncomfortably were independent predictors of non-adherence to ART in Ethiopia. Therefore, healthcare providers, adherence counselors and supporters should detect non-adherence behaviors and patients’ difficulties with ART early, and provide intensive counseling to promote adherence.