Researchers, teachers, and the news media have touted Minecraft as an effective, engaging way to promote students' 21st century skills, including collaboration. However, little is known about what collaboration looks like in Minecraft, including what factors support and undermine high quality collaboration. The current exploratory study investigated this question through an analysis of middle school students' collaborative processes while playing Minecraft in small groups of 2-4 players. Analyses of the discourse functions used by players during gameplay revealed a number of factors affecting the success of their collaboration, such as prior social ties, gaming experience, and responsiveness to other players. The findings contribute new insight into the nature of more and less effective collaborations in multiplayer video games. These insights will be useful to educators who are interested in using Minecraft and other multiplayer games to promote collaboration among their students.