Past studies have found that risk perceptions of suffering from diseases play an important role in the development of intentions to perform physical activity (PA). According to the behaviour motivation hypothesis, perceived risk could be positively and directly related to PA, but this possibility has been ignored and/or underestimated. Accounting for recent methodological developments on the importance of study design and risk perception assessment, the purpose of the present study was to examine the risk-perceptions-PA relationship among older adults. Participants (N = 143) aged from 61 to 70 years initially underwent measurement of risk perceptions, baseline PA, socio-demographic and health factors. Six months later, they were asked about their PA participation. Multiple regression analyses revealed that perceived risk of suffering from diseases and conditions without regular PA participation was an independent positive predictor of later PA, over and beyond baseline behaviour, socio-demographic and health variables. This study fills a gap in the existing literature on the PAs of older adults and reveals that risk perceptions are directly linked to their participation. In addition, it extends existing knowledge in health psychology on the behaviour motivation hypothesis, and emphasises the necessity of methodological adjustments when assessing the risk-perception-behaviour relationship.