In this study, we address the construction of the first symbolic uses of objects in contexts of triadic interaction (adult-child-object). We assume that symbolic productions are based on public rules of the use of objects previously agreed by the community. The first symbols are not rooted in any literal, evident reality, but in shared rules of uses about the material world. We observed six dyads communicating and interacting together with 10 objects in a semi-structured situation longitudinally from 9 to 15?months of age. We found that the infants gradually constructed symbolic meanings, and we identified five symbolic levels and sublevels. At 9?months, the infants attended and engaged in the symbolic uses produced by an adult even though they themselves were not yet able to produce them. At 12?months, infants began to use objects symbolically to communicate with adults. The highest percentage of these first symbolic uses was of level 1, that is, with a close relation to the conventional use of the object used to perform the symbol. At 15?months, children increased their symbolic uses and performed symbolic uses at all levels, whereas adults reduced such practices. Adult semiotic mediation and the social meanings of objects can be considered important factors in children's symbolic productions.