After the failure of a glaucoma drainage device in children, implantation of a second Ahmed glaucoma valve with mitomycin-C allows a significant reduction of intraocular pressure and number of medications with good medium-term and long-term survival. The effectiveness of glaucoma drainage devices (GDD) is limited in time. There is little literature regarding the optimal management strategy after failure of a GDD in pediatric glaucoma. To report the outcomes of Ahmed glaucoma valve implantation (AGV) with mitomycin-C (MMC) after failure of a GDD in children. Retrospective chart review of patients with a history of at least 1 GDD receiving an AGV implantation with MMC between 2000 and 2019. We defined complete success as an IOP of 5-21mmHg without glaucoma medication and qualified success as a final IOP of 5-21mmHg with one or more glaucoma medication, without loss of vision. Twenty-one patients (22 eyes) met the inclusion criteria. The intraocular pressure and number of medications were significantly reduced. The probability of complete success was 47% [95% CI: 29%-75%] at 2 years and 34% [95% CI: 18%-65%] at 4 years. The probability of qualified success was 74% [95% CI: 56%-97%] at 2 years, and 54% [95% CI: 34%-84%] at 5 years. Failure happened in 10 eyes after a mean time of 4.3 years ±3.6 (6mo to 15y), 5 of which (23%) for severe complications or loss of vision. This study of implantation of a second valve with MMC reports a significant decrease in IOP and medications with medium-term and long-term success rates close to those reported for first valve implantation, although with a high risk of complications.