Purpose: The aim of this study is to analyze the changes in temporal synchrony between gesture and speech of multimodal communicative behaviors in the transition from babbling to two-word productions. Method: Ten Spanish-speaking children were observed at 9, 12, 15, and 18 months of age in a semistructured play situation. We longitudinally analyzed the synchrony between gestures and vocal productions and between their prominent parts. We also explored the relationship between gestural-vocal synchrony and independent measures of language development. Results: Results showed that multimodal communicative behaviors tend to be shorter with age, with an increasing overlap of its constituting elements. The same pattern is found when considering the synchrony between the prominent parts. The proportion of overlap between gestural and vocal elements at 15 months of age as well as the proportion of the stroke overlapped with vocalization appear to be related to lexical development 3 months later. Conclusions: These results suggest that children produce gestures and vocalizations as coordinated elements of a single communication system before the transition to the two-word stage. This coordination is related to subsequent lexical development in this period.