Conceptualizing fairness through social psychology theory has recently been called for in classroom assessment (CA) literature. This study used two open-ended questionnaires to explore university students' critical incidents of fairness and unfairness and their affective and behavioral reactions to experiences of un/fairness. The findings showed that students' perceptions of CA fairness were comprised of distributive, procedural, and interactional justice principles. Collectively, students considered the distribution of outcomes, the procedures for outcome distributions, the interpersonal relationships, and the communication procedures in conceptualizing fairness. Students also reported positive feelings such as happiness, satisfaction, feeling valued, and hopefulness when describing fair incidents, while they tended to report negative feelings such as anger, upset, disappointment, and embarrassment as responses to unfair incidents. Students also reported increased classroom engagement and greater adaptation in responses to fairness incidents, while they reported class disengagement, inaction, and dissent as responses to unfair incidents. Building on these empirical findings, a more comprehensive conceptualization of fairness in CA contexts is proposed.