The peat swamp forest is a newly recognized forest formation in the Philippines following its discovery to science in 2005. This paper aimed to present the checklist of plant species in the peat swamp forest of Caimpugan, Agusan del Sur, where such information has been lacking. The checklist was based on the collected specimens during the rapid assessment on November 2010, intensive fieldworks on September 2011 and in the recent site visit on September 2013. One hundred and one (101) species belonging to 56 families and 81 genera were recorded. Tristaniopsis micrantha (Merr.) Peter G. Wilson and J.T. Waterh and Thoracostachyum sumatranum (Miq.) Kurzare were the most dominant species for trees and understory vegetation, respectively. Four (4) species are considered threatened such as Hoya crassicaulis Elmer ex Kloppenb, Huperzia squarrosa (G. Forst.) Trevis., both are endangered while Asplenium nidus L. and Myrmecodia tuberosa Jack are considered vulnerable. The families with the highest number of taxa observed were Rubiaceae (5 genera, 5 species), Orchidaceae (4 genera, 4 species), Euphorbiaceae (4 genera, 4 species), Lauraceae (3 genera, 4 species), Myrtaceae (2 genera, 6 species), Clusiaceae (2 genera, 5 species), Arecaceae (2 genera, 3 species), Pandanaceae (2 genera, 3 species), Poaceae (2 genera, 3 species), Menispermaceae (2 genera 2 species)and Apocynaceae (1 genus, 4 species). The rank abundance of taxa conforms to the observed percent indigenous and endemism pattern of the country based on the framework for Philippine plant conservation strategy action plan of DENR-PAWB.