Materiality remains a challenging concept for auditors to implement in practice. The challenges underlying auditor materiality assessments are compounded by the fact that courts, regulation, and professional standards emphasize that materiality should be based on a “reasonable investor” perspective. Despite the investor orientation and ambiguous nature of the “reasonable investor” criterion, the extant literature lacks empirical evidence about investor materiality judgments and decision-making. To address this problem, we model sophisticated and unsophisticated investors' materiality judgments in a policy-capturing study and compare them to experienced auditors charged with assessing materiality from an investor perspective. The results indicate significant differences in materiality judgments, judgment consensus, and cue utilization among the three participant groups. We conclude the paper with discussion of the study's implications, highlighting that the overall results suggest the need for further consideration of ways to help auditors meet standards and expectations in this critical domain.