Iodine-123 metaiodobenzylguanidine ((123)I-MIBG) can be considered an indicator of pulmonary endothelial cell function. Serial (123)I-MIBG images of the chest were acquired in a patient with high altitude pulmonary edema (HAPE). The initial evaluation was performed 7 days after admission. The lung to upper mediastinum ratios (LMRs) of (123)I-MIBG uptake were 1.33 (for the right lung) and 1.12 (for the left lung). The second examination of (123)I-MIBG lung uptake, which was performed 2 months later, showed LMRs of 1.39 (right lung) and 1.33 (left lung). We speculated that the decreased lung uptake of (123)I-MIBG at the early recovery stage could reflect an impairment in pulmonary endothelial cell metabolic function in the development of HAPE.