Genotoxins cause significant damage to the genetic material of aquatic organisms, requiring rapid and accurate assessment. Fish-derived cells sensitive to genotoxins have proven to be a useful tool for measuring genotoxicity, but the long treatment times required for measurement limit their application in situations requiring rapid testing. Previous studies have shown that fish cells can be kept unstarved for up to 6 h using media containing 1% FBS. In this study, the 1% FBS/6 h parameter was used for genotoxicity assessment. Therefore, genotoxicity assessment was performed after only 6 h of genotoxin treatment in a medium containing 1% FBS. The new genotoxicity assessment method provided faster and more accurate genotoxicity data for climbazole and metolachlor than the existing assessment system using the 15% FBS/96 h parameter. Furthermore, these advantages of the new platform enabled the determination of the genotoxicity of various genotoxins, such as dibenz[a,h]anthracene and ethoprophos. In summary, we have developed a genotoxicity assessment that can generate genotoxicity data rapidly and accurately. This new platform will serve as a foundation for rapid genotoxicity assessment of many genotoxins.