The empirical evidence for why turnout is higher under proportional electoral rules than in plurality systems is mixed. Relying on a quasi-experimental design that occurred in the Polish local elections, we embark on a rigorous empirical test of the effect of electoral rules on turnout. Specifically, we examine municipal elections in Poland (since 1998), where communes above a certain population threshold (i.e. 20000 people) are required to use an Open-list PR system while those below employ the Single-member districts plurality (or First-Past-the-Post), and the Multi-member districts plurality. In addition, to examine the complex relationship between electoral rules and voter turnout, we exploit two recent reforms of the legal rules concerning local elections in Poland, implemented in 2011 and 2018. This allows us to use eg. regression discontinuity design and synthetic control approach in the research on the impact of electoral rules on voter turnout. Moreover, the data that we have collected enable us to move our study beyond the simplification of voting systems as “majoritarian vs. proportional”. While previous quasi-experimental studies have been limited to the electoral systems, which were not simple versions of SMDP or PR, the availability of district-level data for Polish local elections enables us to test the effect of electoral rules on turnout also for simple SMDP/FPTP and PR. Overall, our results suggest that turnout slightly decreases or is unaffected if a polity switches from SMDP to Open-list PR.