Although the global distribution of eumycetozoans in terrestrial ecosystems with varying vegetation types has been a subject of a number of investigations during the past decade, there is still scarce to no available data from the mangrove forests, particularly in the Philippines. Hence, this study assesses and compares the occurrence and distribution of protosteloid amoebae inhabiting the mangrove ecosystem of San Fernando City, La Union, with the villages Biday and Catbangen as representatives. Aerial (AL) and ground (GL) leaf litter samples were used as substrates in isolating protosteloid amoebae and were subjected to moist chamber cultures. The 17 species belonging to 12 genera, from a total of 125 records, were described and reported in this study, with Protostelium mycophagum being the most often occurring species. Further results indicate that the ground microhabitat and the Biday site exhibited higher species diversity and abundance than the aerial microhabitat and the Catbangen site. Regarding species richness in the two leaf litters, GL hosted higher species richness than AL. The current research is one of the few that has assessed and surveyed the eumycetozoan distribution, occurrence, and ecology in the Philippine mangrove ecosystem. Furthermore, it demonstrates the potential for a mangrove forest to support diverse protosteloid amoebae growth.