Previous studies have found that infants shift their attention from the eyes to the mouth of a talker when they enter the canonical babbling phase after 6 months of age. Here, we investigated whether this increased attentional focus on the mouth is mediated by audio‐visual synchrony and linguistic experience. To do so, we tracked eye gaze in 4‐, 6‐, 8‐, 10‐, and 12‐month‐old infants while they were exposed either to desynchronized native or desynchronized non‐native audiovisual fluent speech. Results indicated that, regardless of language, desynchronization disrupted the usual pattern of relative attention to the eyes and mouth found in response to synchronized speech at 10 months but not at any other age. These findings show that audio‐visual synchrony mediates selective attention to a talker's mouth just prior to the emergence of initial language expertise and that it declines in importance once infants become native‐language experts. Studies show that infants shift their relative attention to a talker's eyes and mouth over the course of the first year of life and that these shifts are modulated by whether the talker speaks in a native or non‐native language. We investigated whether the temporal synchrony of the auditory and visual speech that normally emanates from a talker's mouth affects attention by presenting desynchronized native and non‐native audiovisual speech and tracking eye gaze in groups of 4‐, 6‐, 8‐, 10‐, and 12 month‐old infants. Findings showed that desynchronization of both types of speech eliminated the usually observed preference for the talker's mouth at 10 but not at 8 months of age. This indicates that the multisensory redundancy of synchronous audiovisual speech plays a key role in recruiting infant attention to a talker's mouth during the canonical babbling stage, a key phase in the acquisition of speech production capacity.