Three-dimensional (3-D) virtual worlds differ from other learning environments in their similarity to real life, providing opportunities for more effective communication and interaction. With these features, 3-D virtual worlds possess considerable potential to enhance learning opportunities. For effective learning, the users' motivation levels and social presence are important. In this study, the motivation and social presence levels of 42 prospective teachers were measured as they engaged in an Open Simulator 3-D virtual world. Related factors affecting motivation and social presence levels were also examined. An explanatory mixed method design was used in this study. Interviews and three different questionnaires were employed. The quantitative results show that the motivation and social presence levels of the participants were high. The qualitative results also revealed several pertinent factors that are related to motivation and social presence. These factors, which include the particular environment and participant satisfaction, clearly affected motivation while the participants were learning new information. Other factors, such as being relaxed, effective communications, and not feeling lonely in the environment affected the social presence measures. Lastly, the participants perceived the environment as warm and sociable. The results suggest that these factors should be taken into account when 3-D virtual learning environments are being designed.