It is critical to understand how students’ monitoring activities are related to their actions during learning. In particular, studies have not fully explored how students’ spontaneous use of visual representations relate to their perception of its usefulness and their learning outcomes, especially in interactive learning environments. This study, using a math intelligent tutoring system, examines the relations between students’ perceptions of the usefulness of using diagrammatic scaffolding and their actual patterns of spontaneous diagram use in for secondary-school algebra. Results show that students who evaluated diagrams as useful used diagrams more frequently but showed less learning gains, compared to those who evaluated diagrams as not useful and did not use diagrams frequently. We discuss implications of this finding by connecting with prior work that focuses on drawing as diagram use. This study shows the importance of understanding how spontaneous use of diagrams might or might not help student learning.