The present research examined how 3- and 5-year-old Japanese children map novel nouns and verbs onto dynamic action events and generalize them to new instances. Studies 1 to 3 demonstrated that although both 3- and 5-year-olds were able to map novel nouns onto novel objects, only 5-year-olds could generalize verbs solely on the basis of the sameness of the action. Study 4 showed that the difficulty young children experience in learning verbs lies mainly in mapping the appropriate element to a verb rather than in encoding and remembering an action itself. The results of this research are related to a long-debated issue of whether noun learning is privileged over verb learning.