Background: Diphallia occurs once in 5–6 million births, with no two patients presenting with the same anatomical variation. Here we discuss a review of diphallia case reports, as well as present a new surgical classification system based on the soft tissue composition of the two phalluses, the anatomy of the urethra present within the most normal phallus and the bladder configuration. Methods: Eighty-seven diphallia case reports were collected and analysed, excluding those presented in animals and articles that were non-English, with the results compiled to provide an in-depth reference of the specific anatomy found in diphallia patients and the associated abnormalities. Results: Our proposed classification system was then applied to each patient and the most common configuration base on our classification system presented, along with commonly seen associated anomalies. Conclusion: The reviewed cases represent a subset of the most unique diphallia patients; thus, several cases may be left unreported. Future reports can then be categorized, aiding as a reference, and potentially building on the classification, should the patient not fit into a specific group, leading to an expansion of the classification system.