OBJECTIVES: Evidence on the associations between short-term and long-term air temperature exposure and cognitive function in older adults, particularly those in Asia, is limited. We explored the relationships of short-term and long-term air temperature exposure with cognitive function in Taiwanese older adults through a repeated measures survey. DESIGN AND SETTING: We used data the ongoing Taiwan Longitudinal Study on Aging, a multiple-wave nationwide survey. PARTICIPANTS: We identified 1956, 1700, 1248 and 876 older adults in 1996, 1999, 2003 and 2007, respectively. PRIMARY AND SECONDARY OUTCOME MEASURES: Participants' cognitive function assessment was based on the Short Portable Mental Status Questionnaire. We calculated the temperature moving average (TMA) for temperature exposure windows between 1993 and 2007 using data from air quality monitoring stations, depending on the administrative zone of each participant's residence. Generalised linear mixed models were used to examine the effects of short-term and long-term temperature changes on cognitive function. RESULTS: Short-term and long-term temperature exposure was significantly and positively associated with moderate-to-severe cognitive impairment, with the greatest increase in ORs found for 3-year TMAs (OR 1.247; 95% CI 1.107 to 1.404). The higher the quintiles of temperature exposure were, the higher were the ORs. The strongest association found was in long-term TMA exposure (OR 3.674; 95CI 2.103 to 6.417) after covariates were controlled for. CONCLUSIONS: The risk of mild cognitive impairment increased with ambient temperature in community-dwelling older adults in Taiwan.