Abstract: Although regulations requiring labor unions to file financial reports have been in place for more than 60 years, a long-held debate exists about the value of this regulation. Proponents argue that transparency constrains opportunism by union leaders. Others, however, question whether mandated financial disclosures can be used to detect and deter complicated embezzlement schemes in this setting, particularly given the financial illiteracy of rank-and-file union members. Assembling a hand-collected dataset of labor union corruption, I examine the role that mandatory reporting regulation plays in facilitating labor union governance. I find that mandatory reporting can help detect labor union corruption. Further, consistent with the notion that stakeholders do make use of this information, further analysis indicates that the detection and discipline of misconduct increases for the subset of labor unions subject to enhanced disclosure requirements following a 2004 regulation change. Collectively, my findings indicate that mandatory reporting regulation plays a role in combating labor union corruption and, in so doing, suggest that the financial illiteracy of the main audience for these disclosures – as well as the limited governance mechanisms available to union members– does not undermine the value of mandatory financial reporting regulation for labor unions.