Aim of the study: To compare the intraocular pressure (IOP) lowering effect and postoperative complications between primary augmented trabeculectomy and glaucoma drainage device (GDD) implantation as primary surgical intervention in patients with juvenile-onset open angle glaucoma (JOAG). Patients and Methods: A retrospective review study involving 20 eyes that underwent primary augmented trabeculectomy with mitomycin (MMC) and 10 eyes GDD implantation in 3 tertiary centres in Malaysia between 1 January 2013 and 31 December 2019. They were followed up for at least 12 months postsurgical intervention. Intraocular pressure (IOP), number of topical IOP lowering medication and complications were evaluated at 1, 3, 6 and 12 months post-intervention. Based on the IOP, the success was divided into complete and partial success, and failure. IOP and postsurgical complications were compared using the Repetitive Measure Analysis of Variance (RM ANOVA) and the Pearson chi-square test. Results: Both methods were effective in lowering the IOP. Eyes with primary augmented trabeculectomy have significant lower IOP compared to GDD implantation (p = 0.037). There was a higher incidence of postoperative hypotony (30%) in the trabeculectomy group. There was also a significant reduction of mean number of topical pressure-lowering drugs required postoperatively (p = 0.015). Complete success was achieved in 100% of eyes with trabeculectomy and 67% in GDD implantation (p = 0.047). Conclusions: Primary augmented trabeculectomy and GDD implantation are good surgical options for the treatment of JOAG. Both methods provide IOP lowering at 1 year. However, trabeculectomy provides better pressure lowering, compared to GDD implantation in patients with JOAG.