Penile prosthesis implantation is a surgical option for erectile dysfunction when other treatments fail or the patient prefers implantation. Although penile prosthesis is generally considered safe and effective, various complications have been reported in the literature. High-flow priapism, resulting from an arteriovenous fistula between the cavernosal artery and the corpora cavernosa, is a rare complication after penile prosthesis implantation. Managing the condition as autoinflation may lead to unfortunate complications. A 54-year-old male patient underwent a penile prosthesis implantation due to erectile dysfunction lasting for 5 years. Doppler ultrasound revealed arterial insufficiency that was refractory to oral and intracavernosal treatments. A 3-piece inflatable penile prosthesis (Coloplast – Titan) was implanted through a midline penoscrotal incision without any complications. The patient reported uncontrolled tumescence after activating the device, which led us to suspect autoinflation. The final diagnosis was high-flow priapism due to an arteriovenous fistula in the cavernosal artery. The patient was given an antiandrogenic medication and the prosthesis was deflated for 3 months. The fistula closed without any additional intervention. High-flow priapism is a rare but potential complication of penile prosthesis implantation. Careful evaluation and management of patients’ symptoms are necessary for diagnosing and treating this condition. This case highlights the importance of considering high-flow priapism as a potential cause of uncontrolled tumescence after penile prosthesis implantation and the possibility of successful non-surgical management.© 2023. The Author(s), under exclusive licence to Springer Nature Limited.