The development of motor synchrony in dolphins has been described qualitatively, but seldom quantified. We provide a detailed description of the development of synchrony in 12 calves for periods ranging from birth to a few days up to 22 wk. We observed the presence of synchrony, relative positions, and proximity and undertook a videotape analysis of one calf for initiations/terminations of synchrony, response time to breaks in synchrony, and the development of complex behaviors by the calf relative to synchrony. Synchrony was uniformly present more than 90% of the time during month 1, then began to decline gradually. Echelon position was most frequent but calves also spent time in infant position. Initially all calves were most frequently in direct physical contact with their mothers, but by 2 wk of age, all pairs were more likely to be near each other (<0.5 m) without touching. Behavioral complexity increased gradually over the study, and adults frequently performed behaviors during synchronous swimming, providing opportunities for social learning. Synchrony is a predominant behavior in mother-calf interactions, and we speculate that it may be an important mechanism through which calves learn from their mothers via their tandem interactions with the environment.