Corporate scholars have long championed the use of mandatory cumulative voting in developing countries. Yet, in comparison to majority or plurality voting, we know very little about its effectiveness. Even though cumulative voting is allowed in most jurisdictions, in practice it is not widely used. Taiwan stands out as a unique jurisdiction which mandates cumulative voting on all companies. Therefore, Taiwan is the only jurisdiction, to the best of our knowledge, that can be used to test the causal effect of cumulative voting on director election. Taking advantage of an exogenous legal change that occurred in Taiwanese corporate law in December 2011, we use panel data on 640 publicly traded companies from 2009 to 2015 in a difference-in-differences framework to tease out the effect of cumulative voting. From 2001 to 2011, cumulative voting was the default rule, and 20 companies opted for majority voting. While directors and supervisors are elected every three years, not all companies change boards in the same year. Fixed-effect panel regression models show that in the 2012 election—about six months after the legal reform—the cumulative voting rule appears to have weakened the controlling shareholders’ control of the companies that had previously opted for majority voting. The controlling shareholders’ control in the 2013, 2014, and 2015 elections, however, did not decrease. The take-away lesson is that mandating cumulative voting may not create a long-term effect because controlling shareholders find other means to maintain influence. Policymakers should leave the governance decisions to the firm and focus on rules that could restrain private benefits of control and enhance transparency to rein in controlling shareholders.