Introduction: Radiation-induced alopecia (RIA) is a side effect resulting from cranial radiation therapy (RT) and it can be temporary or permanent. In cancer patients, RIA is a less frequent event than chemotherapy-induced alopecia, although the former is more likely to cause permanent hair loss. It is characterized initially by intense anagen effluvium caused by acute dose-dependent damage to the matrix cells of anagen follicles. Proton therapy (PT) is a specific type of RT used in the treatment of brain tumors, which sometimes can cause proton-induced alopecia (PIA), a rare subtype of RIA. Below, we report a case of a patient who presented PIA following PT treatment of a meningioma of the frontal region. Case Presentation: A 38-year-old female patient presented to our trichology outpatient clinic for widespread hair loss in the frontal region. Following a diagnosis of meningioma of the frontal region 3 years ago, adjuvant radiotherapy treatment of the frontal region with scanning beam PT (mean dose of 45 Gy) was performed. Two weeks after the end of treatment, the patient came to our attention with diffuse hair loss at the level of the PT-treated area. Trichoscopy showed flame hairs, broken hairs, black dots, and pigtail hairs. A diagnosis of PIA was established, and topical treatment with minoxidil 5% solution twice a day was initiated. At the follow-up visit after 4 months, the patient had total hair regrowth. Conclusion: PIA is a subtype of RIA still poorly studied in the literature. Hair loss is caused by aggression by radiations of the hair follicle in the anagen phase, leading to an interruption of the mitotic activity of the matrix cells. The cells of the follicular bulb are characterized by marked mitotic activity at this stage and are consequently more susceptible to cytotoxic damage. All this causes tightening of the proximal portion of the hair shaft, increasing its fragility and susceptibility to breakage.