Wiki technology has been promoted as a collaborative software platform. This study investigates interactions that occur in a wiki-based collaborative learning project. The study draws on interaction literature and investigates the types of interactions with which students are engaged in wiki-based group projects, clusters that reflect online interaction patterns and factors that affect students' interaction. The study employs a quantitative approach (principal component analysis, cluster analysis and Kruskal-Wallis test) and a qualitative approach (interviews). The results show that students' interactions online were of two types, student-content and student-student, with student-content interaction being dominant. An increase in online interaction was driven mainly by an increase in student-content interaction, while student-student interaction increased to a certain level and then stayed the same. The study also discusses factors that influenced both types of interaction and suggests guidelines on how student-student interaction can be encouraged.