The Weiss score is the reference method to distinguish between a benign and a malignant adrenocortical tumor (ACT). A program was initiated to improve the reproducibility of the pathologic diagnosis of ACTs in France through the National INCa-COMETE Network. Twelve pathologists from all Reference Centers of the Network analyzed 50 selected ACTs using a web-based virtual microscopy approach in a blind design, allowing to determine the intraobserver and interobserver reproducibilities of the Weiss system. All ACTs were read twice in random order before and after a coaching meeting organized to harmonize and improve analyses and create an online tutorial. The validity of the virtual approach was first established by comparing the 2 consensuses (virtual and microscopic) obtained for each tumor by 3 pathologists who performed the 2 approaches in a blinded manner. For the "dichotomized Weiss score" (separating malignant ≥3 from benign ≤2 tumors) interobserver reproducibility was "substantial" at the first "virtual" reading (κ = 0.70) and increased at the second "virtual" reading (κ = 0.75). In parallel, 7 of the 9 items of the Weiss system showed improvement. The diagnostic accuracy of the observers as a group, using the modal group score approach, showed an improved sensitivity from 86% to 95% for the diagnosis of malignant ACTs. We show the validity of the virtual microscopy approach and that the program improved the practice of the Weiss system reading and therefore the diagnosis of ACT. This tool can now be extended for other research and/or routine purposes in this rare cancer.