The high prevalence of pulmonary hypertension (PH) in elderly patients is well known. However, much remains unknown about those population. We sought to find the clinical characteristics of echocardiographic PH and the prognostic factors in patients ≥90 years of age. We retrospectively reviewed 310 patients ≥90 years of age (median age 92 years, 64% women) diagnosed as echocardiographic PH (peak systolic pulmonary arterial pressure ≥40 mm Hg) with normal left ventricular systolic function. We defined left heart disease (LHD) as significant left-sided valve diseases, left ventricular hypertrophy and left ventricular diastolic dysfunction by using echocardiography. The endpoint was all-cause death at 2,000 days after diagnosis. LHD was found in 92% of patients. During the median follow-up of 367 days (interquartile range, 39-1,028 days), 151 all-cause deaths (49%) occurred. Multivariable Cox regression analysis demonstrated that right ventricular fraction area change <35% (adjusted hazard ratio [HR]: 2.31; p <0.001), pericardial effusion (adjusted HR: 2.28; p <0.001), serum albumin <3.5 g/dL (adjusted HR: 1.76; p = 0.001), chronic obstructive pulmonary disease (adjusted HR: 1.93; p = 0.001) and New York Heart Association (NYHA) class ≥II (adjusted HR: 1.73; p = 0.004) were associated with mortality after adjusted for age. In conclusion, LHD was significantly associated with echocardiographic PH in most patients ≥90 years of age. Also, the co-morbid factors at diagnosis (right ventricular systolic dysfunction, pericardial effusion, hypoalbuminemia, chronic obstructive pulmonary disease, and NYHA class ≥II) were independently associated with mortality.