Although diagrams have been shown to be effective tools for promoting understanding and successful problem solving, students' poor diagram use has been identified as a serious issue in educational practice-related reports. To enhance students' diagram construction skills and to address problems in diagram use, creating learning situations that make it inevitable for students to use diagrams would likely be helpful. To realize this, communicative learning situations can be considered a viable option, as students would feel a greater necessity to use diagrams as a consequence of feedback they receive while explaining. Thus, this study examined the hypothesis that an interactive peer instructional learning situation would better promote students' spontaneous diagram use compared to a non-interactive situation. Eighty-eight university students were randomly assigned to one of two conditions: interactive and non-interactive. After reading a passage relating to the science and engineering area, participants in the interactive condition were requested to explain the content of the passage to another participant next to them. In contrast, participants in the non-interactive condition were asked to record an explanation using an IC recorder by imagining that they were explaining to another person. A sheet of paper was provided to participants during the explanation, and diagram use on the paper was analyzed. The results revealed that students' diagram use in the interactive condition was higher than in the non-interactive condition. This indicates that teachers' provision of interactive communication situations can effectively promote students' likelihood of using diagrams spontaneously.