The efficacy of chemical disinfectants is reduced owing to the inactivation of active ingredients after dilution. This study investigated the effect of time on the efficacy of six different disinfectants, after dilution, against avian influenza virus. When used at the recommended concentration, most disinfectants showed efficacy at a high concentrations in the presence of organic materials immediately after dilution, while sodium dichloroisocyanurate-based products, after dilution, showed reduced efficacy over time at low concentrations in the absence of organic materials. Most disinfectants were neutralized by organic materials; however, this could be compensated for by increasing the product dosage. For successful decontamination in farms, disinfectants should be used at high concentrations in accordance with the manufacturers’ recommendations. Furthermore, the presence of organic materials must be taken into consideration, and diluted disinfectant solution should be prepared no more than a day before use.