Neurofibromatosis type 1 (NF1) has no current effective treatments beyond surgery. Topical photodynamic therapy (PDT) has the potential to provide a less invasive treatment modality. Based on murine data, we hypothesized PDT could be used for the treatment of cutaneous neurofibromas (cNF). We conducted a phase I trial to examine absorption and conversion of topical aminolevulinic acid (ALA) in cNF and determine safety in a dose escalation study. ALA or control vehicle was applied to neurofibromas through microneedle-assisted delivery ( = 4) and excised specimens were examined 24 h later for protoporphyrin IX fluorescence. Fluorescence was detected in the tumors at 304 ± 94 U/μm, while adjacent paralesional normal skin and vehicle-treated tumors showed no fluorescence ( < 0.0001). Subsequently, neurofibromas ( = 27) were treated with ALA and irradiated with 633 nm red light 18 h later, at escalating dosages of 50 and 100 mJ/cm. Maximum tolerable dose was established at 100 mJ/cm. Light microscopy study of tumors biopsied 48 h after PDT (ALA  = 14 and vehicle  = 4) showed mixed inflammatory infiltrate in the ALA, but not in the vehicle-treated tumors or perilesional normal skin. TUNEL evaluation showed 42.5 ± 19.9 apoptotic cells per visual field for ALA-treated and 1.1 ± 1.4 for vehicle-treated tumors ( = 0.002). In the first reported clinical trial of PDT for NF1, PDT targeted neurofibromas specifically, and may offer a normal tissue-sparing treatment modality in the future. This study is registered at Clintrials.gov (NCT01682811).