Background: supernumerary thumb phalanges are rare congenital anomalies within the spectrum of preaxial polydactyly. Although commonly classified using the Wassel system, atypical variants that do not conform to this classification present diagnostic and surgical challenges. These anomalies may occur as isolated findings or in association with syndromic conditions and can affect both function and aesthetics. Case Presentation: we report the case of a 2-year-old male presenting with an isolated supernumerary phalanx on the radial aspect of the right thumb. Clinical examination demonstrated a well-formed accessory structure without functional impairment. Radiographic evaluation, including anteroposterior and oblique views, revealed a fully ossified accessory phalanx without joint or metacarpal duplication, consistent with an atypical form of preaxial polydactyly not classifiable within the Wassel system. Surgical excision was performed with preservation of ligamentous, tendinous, and neurovascular structures. Postoperative follow-up showed excellent functional and cosmetic outcomes, with full range of motion and proper thumb alignment. Methods: a narrative literature review was conducted using PubMed, Google Scholar, and Cochrane Library databases. A total of 32 articles were identified, of which 15 were selected based on relevance. Search terms included: “supernumerary thumb phalanx,” “radial polydactyly,” “thumb duplication,” “preaxial polydactyly,” “pediatric hand surgery,” and “surgical treatment.” Results: the Wassel classification remains the most widely used system for thumb duplication; however, atypical presentations are increasingly recognized. Imaging plays a critical role in identifying anatomical variations and guiding surgical planning. Evidence suggests that early, anatomically guided surgical excision yields favorable functional and aesthetic outcomes. Conclusion: isolated supernumerary thumb phalanges represent a rare and atypical form of preaxial polydactyly that may not fit existing classification systems. Individualized surgical management based on detailed anatomical assessment is essential to achieve optimal outcomes. This case highlights the limitations of traditional classifications and reinforces the importance of tailored surgical strategies.