Background: Dientamoeba fragilis is a pathogenic trichomonad parasite found in the gastrointestinal tract of humans and is implicated as a cause of diarrheal disease. Previous studies led to the discovery of virus- like particles (VLPs) in D. fragilis. Aims: The objective of this study was to describe, by transmission electron microscopy, the presence and morphological details of the virus population found in different clinical isolates of D. fragilis growing in xenic culture. Methods: Transmission electron microscopy (TEM) of thin sections made from trophozoites and negative staining of VLPs in growth media was used to determine their characteristics. Results: These heterogeneous virus populations comprise different sizes ranging from 33-40 nm and most common shape was spherical. These VLPs contain an inner dark core surrounded by an electron-lucent layer and an electron dense capsid coat. Dientamoeba fragilis VLPs are mainly found outside the nucleus in the perinuclear region of the trophozoite. In addition, virus particles were observed to be associated with the Golgi in the perinuclear region while other VLPs were found in the vicinity of parasite plasma membrane. These VLPs attach and penetrate into D. fragilis by endocytosis. Internally, VLPs are commonly seen in lysosomes which may be where viral uncoating occurs. Virus-like particles were abundant in the growth media of stationary-phase cultures of D. fragilis. Virus-like particles were found in growth media of four isolates of D. fragilis. Dientamoeba fragilis VLPs are detectable in dying trophozoites present in in vitro cultures. Conclusion: Whether viral load contributes to cell death is unknown. The identity of the viral genome was also studied. Unlike Trichomonas vaginalis, D. fragilis trophozoites do not contain an abundant viral dsRNA.