The kissing loach, an endangered species surviving only in a few Japanese rivers, spawns in the rice-field areas after migration from rivers in early June. To characterize the environmental conditions required for spawning of the kissing loach, spawning was assessed for two years both by direct observation of spawning behavior and by the appearance of eggs, larvae, and juveniles from June to October. All spawning of the kissing loach was limited to within a couple of days after the formation of temporary waters by remarkable rises in water level. Water temperature and daily rainfall fluctuated during the investigation periods, and no clear relationships with spawning were detected. Furthermore, all spawning was observed only in temporary waters with terrestrial grasses. Thus, spawning of the kissing loach is rigidly limited spatiotemporally to after the formation of temporary waters over terrestrial vegetation. Appropriate management of temporary waters will be crucial for the continued existence of this species.