Mathematical reasoning involves comprehending mathematical information and concepts in a logical way and forming conclusions and generalizations based on this comprehension. Computer-based learning has been incorporated into classrooms across the country, and specific aspects of technology need to be studied to determine how programs are influencing student reasoning and learning. This article explores how one aspect of computer-based learning, electronic support tools (ESTs), influences students' mathematical reasoning over the course of an online supplemental mathematics program, the Math Learning Companion (MLC). Students in Grades 3, 4, and 5 (N = 31) from two private schools participated in MLC, and their reasoning was assessed before and after participating in the program. EST use was measured by using frequency counts for each tool. Results describe students' tool use and reflect an overall change in their reasoning over the course of the intervention, indicating that students use ESTs as needed to individualize the learning program. Students specifically used ESTs as needed to improve their mathematical reasoning, their correctness of response, and their mathematical explanations of their answers over the course of the intervention.