Teachers' conceptions of fairness influence their approaches to assessment. Perceptions of fairness underpin how teachers legitimate their values and provide reasons for teachers to defend assessment decisions and actions. This study therefore examined fairness conceptions at a critical stage in teachers' journey towards assessment capacity: their perceptions as teacher candidates. Specifically, we investigated 228 preservice teachers' conceptions of assessment fairness using the Classroom Assessment Fairness Inventory (CAFI). The results of an exploratory factor analysis (EFA) showed four factors: "assessment communication acts," "grading decisions," "responses to cheating" and "firm assessment decisions." These factors highlighted the domains and underpinning principles of fairness that participating preservice teachers used to evaluate issues of fairness in assessment. The results provide initial empirical foundations to promote nuanced understandings of fairness in assessment education.