In order to identify an indoor thermally comfortable environment for older people, this study examined the thermal acceptance of 384 older people of ages from 60 to 97 years under various thermal environmental conditions in 19 centers for older people in Hong Kong. The results were compared to those of the younger residents in Hong Kong. A probable decay of one predicted mean vote (PMV) for every 25.3 years was reported for older people beyond the age of 60 years ( p ≤ 0.05), which indicated that the older age group probably has a different expectation of a thermoneutral environment as compared with younger age groups. It was also noted that the expected PMV for a thermoneutral environment of older females was apparently higher than that for older males in the same age group. The results should be a useful reference for an acceptable thermally comfortable environment in centers for older people up to the age group over 90 years.