With the popularization of massive open online courses (MOOCs) in the e-learning landscape, more and more older adults are participating in MOOC learning activities. Understanding older adults' learning motivations in MOOCs will help MOOC developers design suitable learning systems and appropriate course content for older learners. Using a content analysis method, this study identifies six types of learning motivations of older adults in MOOCs: solving problems, acquiring knowledge, improving cognition, seeking fun, benefiting others, and social contact, among which improving cognition is unique to older adults. Based on the above classification, we found that the learning motivations among older adults vary with age and gender. The findings enrich the theories of education for older adults and of learning motivation, and can be used to improve the design of MOOCs for older adults.