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 financial reporting information can be used to detect and deter complicated misconduct schemes in this setting. Assembling a hand-collected dataset of labor union misconduct, I examine the role that financial reporting plays in detecting union misconduct. I find that financial reporting information can be used to detect labor union misconduct. Consistent with the notion that stakeholders do make use of this information, further analysis indicates that the detection and discipline of misconduct increase for the subset of labor unions subject to enhanced reporting requirements following a 2004 regulation change. Collectively, my findings indicate that financial reporting information plays a role in combating labor union misconduct.