Aim: We aimed to investigate the adipogenic effects of adenovirus (Ad) serotypes 5, 36 and 8 in a Colo-320 cell line using histochemical, immunohistochemical and electron microscopic methods. Materials & methods: Ad serotypes were inoculated in a Colo-320 cell line and were cultured for 14 days. They were then collected and fixed with 4% paraformaldehyde to analyze their adipogenic effects using histochemistry, immunohistochemistry and electron microscopic methods. Intracellular lipid droplets were detected in the Colo-320 cells inoculated with Ad36 and Ad5 by electron microscopic analyses. Results: After Oil Red O staining, the pink-orange staining was positive intracellularly in Colo-320 cells infected with Ad36 and Ad5. In addition, the leptin immunoreactivity was also positive in these cells. Conclusion: Our results suggested that intracellular lipid accumulation occured after infection with Ad36 and Ad5. The positive staining of Oil Red O and leptin also supported the electron microscopic results; therefore, we conclude that this accumulation occurred due to adipogenic effects of Ad36 and Ad5.