Neurofibromatosis type I (NF1) is an autosomal dominant neurocutaneous disorder characterized by a mutation in the NF1 gene, leading to loss of neurofibromin function and subsequent hyperactivation of the Ras-MAPK signaling pathway. Early diagnosis is critical to initiate appropriate surveillance and therapeutic interventions, yet clinical recognition can be challenging due to phenotypic variability and frequent de novo mutations. This case highlights a 17-year-old male with a delayed NF1 diagnosis due to initially inconclusive clinical features and limited family history. The diagnosis was confirmed only after the development of multiple hallmark findings, including café-au-lait macules, axillary freckling, Lisch nodules, and a symptomatic plexiform neurofibroma. The delay in diagnosis resulted in missed opportunities for early intervention and surveillance. The patient was eventually started on selumetinib, a mitogen-activated protein kinase inhibitor approved for inoperable plexiform neurofibromas. This case underscores the importance of early clinical suspicion, timely genetic confirmation, and multidisciplinary management to improve outcomes in NF1.