To investigate outcomes of trabeculectomy ab externo in African ancestry primary open-angle glaucoma (POAG) patients, and to analyze the impact of demographic and phenotypic factors on surgical success and complication rates. A retrospective case-control study enrolled 63 eyes of 55 POAG cases who underwent trabeculectomy ab externo. Data on demographics, family glaucoma history, surgical specifics, and pre/postoperative measures (intraocular pressure, visual acuity, visual field, medication usage, complications within one year) were collected. Analysis included linear/logistic regression models adjusting for inter-eye correlation. Trabeculectomy yielded success without additional medication in 46%, qualified success with medication in 22%, and surgical failure necessitating further intervention in 32% within one year. Subjects experienced reduction in intraocular pressure (IOP) (46%), daily glaucoma medication (73%), and eye drop usage (67%) 1-year post-trabeculectomy (all P<0.001). However, there was a postoperative decline of 56% in visual acuity (VA) (P<0.001) and a significant worsening of visual field parameters, including a 14% decrease in mean deviation (P=0.02) and a 19% decrease in visual field index (P=0.004). Top of FormBottom of Form59% of patient eyes experienced complications within one year of surgery. Univariate analysis of predictive factors for surgical outcomes revealed that younger age at surgery (P=0.01) and family history of glaucoma (P=0.046) were predictive of lower rates of surgical success. Multivariable analysis revealed worse preoperative VA (OR 0.79 per 0.1 LogMAR increases, P=0.02) was associated with lower likelihood of surgical success. This study underscores the low rates of trabeculectomy success and high rates of complications in an African ancestry population with POAG. While the procedure exhibited positive effects on IOP control and medication reduction, our analysis found that multiple factors, particularly age, family history, and worse preoperative VA play crucial roles in influencing surgical success. Trabeculectomy in African ancestry individuals with primary open-angle glaucoma shows a 46% success rate and frequent complications, indicating that younger age and family history are significant predictors of surgical failure in this high-risk population.