<p>Massive open online courses (MOOCs) offer a unique opportunity for lifelong learning by providing a learning platform for a large and diverse audience. Although their popularity is still growing, industry experts had anticipated a higher level of acceptance than has actually occurred. One possible reason for the slower-than-expected growth is the perceived risk to learners. This study examines the factors influencing MOOC adoption based on perceived risk theory. Using survey-based quantitative analysis (with responses from 300 university students), the authors define four main dimensions of perceived risk: value, non-financial investment, social risk and security. Their findings show that uncertainty about the value offered by MOOCs is one of the most important dimensions in assessing risk. The second most important risk factor is learners’ non-financial investment. The main sources of this investment, time and effort, are finite for learners and thus represent a critical dimension in the educational context of risk research. Social factors also have an impact on perceived risk, albeit to a lesser extent, while security factors do not. The results suggest that MOOC developers and providers play an important role in reducing risks associated with delivery uncertainty and in optimising learners’ time and energy.</p>