Purpose: To report a case of high-altitude cerebral edema and high-altitude retinopathy resulting in persistent neurologic and long-term visual sequelae following inadequate acclimatization. Methods: A single case was reviewed. Results: A 32-year-old man developed high-altitude sickness during a hike in the Andes, most likely due to inadequate acclimatization during ascent. He was diagnosed with high-altitude cerebral edema and high-altitude retinopathy. Neurologic deficits persisted during the 4-day stay at high altitude but resolved immediately after descent below 4300 m; however, multiple cerebral hemorrhages remained visible on magnetic resonance imaging. Severe bilateral macular hemorrhage led to prolonged vision loss lasting several months. Both eyes subsequently developed macular epiretinal membranes, with a macular hole in the right eye requiring vitrectomy. Although intraretinal hemorrhages in the posterior pole resolved, multifocal electroretinography demonstrated numerous persistent areas of reduced retinal response density for several months. Conclusions: Adequate acclimatization is essential for preventing high-altitude sickness, even in experienced climbers. High-altitude retinopathy may result in permanent vision loss; therefore, long-term ophthalmologic monitoring is recommended.