• Context.-Acute invasive fungal sinusitis (AIFS) can be challenging to diagnose because of its varied clinical presentation. Objectives.-To evaluate the discrepancies between clinical and autopsy diagnoses in patients with histologic evidence of AIFS at a tertiary care center. Design.-Autopsy cases with a pathologic autopsy diagnosis of AIFS from the past 20 years at a tertiary hospital were evaluated for clinicopathologic features. Modified Goldman classification was used to classify discrepant cases. Clinical history was also reviewed. Results.-Of 7071 institutional autopsy cases during 20 years, 9 met inclusion criteria and demonstrated AIFS at autopsy. Angioinvasive fungal elements were histologically identified in all cases, with multiorgan involvement in most cases (6 of 9; 67%). Major clinicopathologic discrepancies were identified in 6 cases (67%). Conclusions.-AIFS is an uncommon diagnosis rendered at autopsy. There is a subset of cases that demonstrate discrepancy between the clinical impression and pathologic autopsy diagnosis. Antemortem diagnosis of AIFS can be challenging, especially in cases without prototypical clinical symptoms and positive fungal cultures. At autopsy, there was multiorgan involvement, supporting extensive tissue sampling to evaluate for AIFS, even in the setting of negative fungal cultures or lack of classic symptoms. These findings highlight the importance of the pathologist's role at autopsy in the definitive diagnosis of AIFS, especially in clinically equivocal cases.