House presents special problems for design in relation to climate as it accommodates variety of uses over 24-hour period. It is widely known in the tropical countries that traditional houses are more sensitive to the prevailing climate and able to provide comfortable internal environment for the occupants. Tambi as one of traditional houses in upland Central Celebes Indonesia is believed to be thermally comfortable, yet there still no empirical evidence to approve it. Present study conducted empirical studies on typical traditional Tambi houses to evaluate their thermal performance. External and internal climatic conditions were measured in each house and were analysed. Results of the study showed that typical traditional Tambi house are not able to maintain the internal temperature within the comfort range for a preiod of 24hours. Thermal quality of the house, however, were improving as indicated by internal temperatures which were more satisfactory than the external temperatures. Keywords-thermal performance, traditional tambi house, tropical upland climate Abstrak-Rumah dari sudut pandang tertentu dianggap sebagai representasi desain dalam hubungannya dengan kondisi iklim dan berbagai macam penggunaan ruang. Rumah tradisional di negara-negara tropis secara umum dipandang lebih tanggap terhadap iklim setempat serta dapat memberikan lingkungan internal yang nyaman bagi penghuninya. Rumah tradisional Tambi yang berada di dataran tinggi Sulawesi Tengah, Indonesia adalah salah satu contohnya. Meskipun secara empiris belum terbukti, rumah Tambi diyakini memiliki kenyamanan termal yang baik. Penelitian ini dilakukan untuk melihat kinerja termal rumah tradisional Tambi. Melalui studi lapangan, kondisi iklim internal dan eksternal pada setiap rumah direkam dan dianalisa. Hasil penelitian menunjukkan bahwa Rumah Tambi sudah dapat meningkatkan kualitas termal bangunan, namun belum mampu mempertahankan kondisi ruang dalam agar senantiasa nyaman selama periode 24 jam.