Amphipods in the genus Cerapus are tube-dwelling amphipods and commonly found in coastal habitats. In the present study, a Crepaus sp. was found in the Mae Klong River mouth, Amphawa District, Samut Songkhram Province, Thailand. Herein, the gut contents of Crepaus sp. were investigated by twenty individuals (10 males and 10 females). The major food items were fungus, algae, diatom, organic substance, and protozoa. There was no difference of food contents in both sexes. In summary, Cerapus sp. can be considered as a suspension feeder and detritus feeder.