This study examines why university students are willing, or unwilling, to use formal reporting channels when encountering integrity-related misconduct. Drawing on new institutionalism, it links formal institutional evaluation, informal normative environment, boundary cognition, tolerance of integrity violations, and reporting willingness. Based on an anonymous survey of 331 students from four universities in Beijing and a structural equation model, the results show that satisfaction with integrity governance significantly increases reporting willingness. Perceived prevalence of integrity-risk practices also has a positive direct effect, suggesting that problem awareness may activate students’ sense of responsibility. Boundary cognition does not directly predict reporting willingness, but it reduces tolerance, which in turn increases reporting willingness. Tolerance therefore operates as a complete mediator in the cognition path and as a suppressing mechanism in the perceived-prevalence path. The findings indicate that university integrity education should focus on attitude formation, safe reporting procedures, and confidence in formal channels.