Although group project concepts and skills have become a major component in most information systems (IS) academic programs, very little research has attempted to examine factors that may improve or undermine effectiveness of IS group projects. Accordingly, based on relevant literatures, this study develops and empirically tests a model of factors affecting IS group project effectiveness. The research model posits that group cohesion and group efficacy will have positive effects on group effectiveness (project success and expected impact), whereas perceived loafing is expected to have a negative effect on IS group effectiveness. Data collected from 104 students working in 29 groups to complete semester-long projects in two IS courses revealed that group efficacy had positive impact on group effectiveness and perceived loafing demonstrated a partial effect. Contrary to expectations, the impact of group cohesion was nonsignificant. These results could be useful in evaluating groups' potential for success and creating conditions conducive to enhancing effectiveness and success of IS student group projects.