There are relatively few studies examining cooperative learning during laboratory activities in a science museum. This study aims to explore such activities to better understand the nature of cooperative learning, if any, in that setting. The participants in this study were 60 fourth-grade students who visited a science museum lab as part of a school field trip. The students, divided into 12 groups, were videotaped and audio-recorded during group work consisting of balancing a scale. Our inductive data analysis of the observations revealed that although each group's interactions were distinctive, common themes emerged. Moreover, even though the group work required cooperative learning, students did not engage in such. Students mostly instructed each other on how to operate the scale, with no scientific explanations. As the students did not know how to work together in order to solve the task, frustration abounded. This research adds to the body of knowledge about lab activities in science museum and offer practical implication to design more effective activities in these settings. Careful pedagogy and thoughtful facilitation can contribute to the students' learning outcomes; therefore, educators should consider the following: ensuring students have sufficient prior knowledge, having the museum educator play the role of a mediator, taking steps to reduce the level of student frustration, and planning additional activities that promote the learning outcomes of the activity.