We investigated when children acquire class extension rules for denominal verbs and deverbal nouns using an intermodal preferential looking paradigm. We taught French-speaking 2.5-year-olds (mean age = 2 years, 8.56 months [2;8.56], range = 2;6–2;11) and 3-year-olds (mean age = 3;3.31, range = 3;0–3;5) novel parent nouns or verbs referring to unfamiliar instruments and their functions, and then tested their interpretation of both the parent word and its denominal verb or deverbal noun. Experiment 1 demonstrated that only the 3-year-olds understood the denominal verbs. Experiment 2 demonstrated that only 3-year-olds who learned the parent verbs were able to interpret the deverbal nouns correctly. These findings suggest that French-speaking children acquire class extension rules for denominal verbs and deverbal nouns by the age of 3 years and can demonstrate this knowledge as long as they are able to learn the parent words.