The study investigates how basic communicative functions expressed by utterance modalities (declarative, exclamative, injunctive, interrogative) emerged in the early language of a French child, and examines whether and how morphosyntactic and prosodic devices were used to mark these contrasts. A longitudinal corpus of naturalistic productions was collected between the ages of 1;2 and 1;9, and 960 utterances were subjected to functional, prosodic and grammatical analyses. Declarative, exclamative and injunctive utterances were found from 1;2, and first interrogatives appeared at 1;6. Intonation contours varied as a function of utterance modality and were largely in accordance with the patterns in French: declaratives and exclamatives were falling, interrogatives rising and injunctives split between falling and rising contours depending on their specific functions. A quarter of the productions involved an elementary grammatical marking of utterance modality such as interjections, imperative or indicative verbal forms, or interrogative morphemes. These findings indicate an early and complementary use of prosodic and grammatical devices in the child's construction of the linguistic system.