Previous research has made it clear that older learners are mainly learning for learning's sake. However, few studies have explored the intrinsic aspects of older learners' motivation in detail; also, the factors that influence their learning motivation remain under-researched and under-theorised. To address this gap, this survey-based quantitative study investigated the learning motivations of 816 older learners from an intrinsic-motivation viewpoint, and explored the predictors of these motivations, including institutional as well as personal factors. The results indicated that these older learners rated their intrinsic motivations highly (3.97/5 overall), and that such motivations could be differentiated into cognitive-oriented and social-oriented motivations. The most important predictors of intrinsic motivations for the respondents were institutional variables, especially teacher support and peer support. Importantly, institutional predictor variables were found to diminish the negative impacts of both self-reported poor health and age on these older adults' overall intrinsic motivation to learn. These findings imply that, in Taiwan, providing more teacher- and peer support is likely to increase the intrinsic motivation to learn for vulnerable older adults who are disadvantaged by health problems and old age.