Existing studies have paid a great deal of attention to how electoral systems affect party politics, but there has been little discussion in the literature on the effects of party registration rules. The theoretical importance of the impact of party registration rules on party system development lies in its temporal priority to the effects of electoral systems. This study aims to fill the theoretical void by conducting a systematic analysis of the effects of party registration rules in Latin America. Using an original dataset of petition signature requirements and spatial registration requirements in 18 Latin American countries from 1978 to 2011, I conduct cross-national time-series analyses on how this institution affects the number of parties. The empirical results show that a more restrictive petition signature requirement significantly reduces the number of electoral parties in a country, while a spatial registration requirement does not significantly affect the number of parties.