The objective of this study was to investigate the biodegradation of ethylene in an activated carbon biofilter inoculated with immobilized microbial consortium. The biofilter performance was monitored in terms of ethylene removal efficiency and carbon dioxide production. The biofilter was capable of achieving ethylene removal efficiency as much as 100% at a residence time of 14 min and an inlet concentration of 290 ppm. Under the same conditions, carbon dioxide with a concentration of up to 546 ppm was produced. Its was found that carbon dioxide was produced at a rate of 87 mg day$^$-1/, which corresponded to a volume of 0.05 L day$^$-1/. During operation with an inlet ethylene of 290 ppm, the maximum elimination capacity of the biofilter was 34 g of C$_2$H$_4$m$^$-3/ day$^$-1/. The biofilter could provide an attractive treatment technology for removing ethylene, an extremely volatile and slowly adsorbed compound.