Older people are very likely to experience transitions among spaces with different temperatures in daily life. But little has been known about their thermal comfort and physiological responses to these temperature steps. This study investigated 18 healthy older people's thermal perceptions and physiological parameters under cold and warm exposures with 3/5/6 °C temperature steps. The results showed that subjects' thermal sensation was sensitive to all moderate temperature steps, but their thermal comfort perception could only distinguish temperature changes greater than 5 °C. Thermal unacceptability was only observed when subjects' tympanic temperature reached at 37.08 °C. Also, we found older people need more than 50 min time to get their mean skin temperature steady after cold stimuli, while they only need <24 min after warm ones. Cold stimuli could significantly boost subjects' blood pressure, respiratory rate, blood oxygen saturation, and depress heart rate. To predict older people's transient thermal sensation after temperature steps, we proposed two regression models for cold and warm exposures respectively. Based on the above observations, we suggest older people should try their best to avoid large step temperature changes, especially for cold side steps.