The peninsular effect is a geographical phenomenon that explains patterns of species richness. Hypotheses regarding the peninsular effect in bird taxa should be more focused on testing not only recent deterministic processes but also migrant inflow associated with recent environmental variations. We aimed to identify the latitudinal patterns of passerine species richness and test hypotheses regarding recent deterministic processes (climate, primary productivity, habitat diversity, forest area, and anthropogenic disturbances) and migration influence (ratio of migrant species richness) in the Korean peninsula. We used the distribution data of 147 passerine species from 2006 to 2012. Single regression between passerine species richness and latitude supported the existence of the peninsular effect. Mean temperature induced by latitude gradient negatively affected LAI and forest area, and positively habitat diversity. However, passerine species richness was only influenced by LAI and forest area. Ratio of migrant species richness increased as decreasing habitat diversity and was not influenced by LAI and forest area. And we found that ratio of migrant species richness increased with increasing latitude, and contributed to the increasing in passerine species richness. No. of patches did not influenced passerine species richness. These results support the existence of the peninsular effect in the distribution of passerine birds induced by recent deterministic processes such as primary productivity and habitat area, and migrant species inflow caused by competition.