The paper presents a comparative study of the climate responsive design strategies and indoor thermal performance of three vernacular houses in Guanshan Township of eastern Taiwan by building survey and instrument measurements. These houses are all about 80 years old. They are of Chinese style, Japanese style, and a mixture of both styles. All three houses are popular building types in the region. Key findings include: (1) Space buffer, thermal insulation, ground exposure, and natural ventilation are the key elements of climate responsive design strategies. (2) The climate responsive design strategies of the three buildings, while using similar building material, are not the same. They are strongly associated with the buildings’ cultural roots as well as the buildings’ use patterns. (3) The Chinese-style house is a heat rejecter. It is comfortable in spring and summer. The mixed-style house is a heat keeper. It is comfortable in winter and spring. The Japanese-style house is well-ventilated and has equal thermal comfort level at around 50% in all seasons. It is uncommon that vernacular buildings from different cultural traditions coexist in the same region. This study provides detail appraisals of their respective sustainable design strategies in hot and humid climate.