Temporal proximity is one of the key factors determining whether events in different modalities are integrated into a unified percept. Sensitivity to audiovisual temporal asynchrony has been studied in adults in great detail. However, how such sensitivity matures during childhood is poorly understood. We examined perception of audiovisual temporal asynchrony in 7- to 8-year-olds, 10- to 11-year-olds, and adults by using a simultaneity judgment task (SJT). Additionally, we evaluated whether nonverbal intelligence, verbal ability, attention skills, or age influenced children's performance. On each trial, participants saw an explosion-shaped figure and heard a 2-kHz pure tone. These occurred at the following stimulus onset asynchronies (SOAs): 0, 100, 200, 300, 400, and 500 ms. In half of all trials, the visual stimulus appeared first (VA condition), and in the other half, the auditory stimulus appeared first (AV condition). Both groups of children were significantly more likely than adults to perceive asynchronous events as synchronous at all SOAs exceeding 100 ms, in both VA and AV conditions. Furthermore, only adults exhibited a significant shortening of reaction time (RT) at long SOAs compared to medium SOAs. Sensitivities to the VA and AV temporal asynchronies showed different developmental trajectories, with 10- to 11-year-olds outperforming 7- to 8-year-olds at the 300- to 500-ms SOAs, but only in the AV condition. Lastly, age was the only predictor of children's performance on the SJT. These results provide an important baseline against which children with developmental disorders associated with impaired audiovisual temporal function--such as autism, specific language impairment, and dyslexia--may be compared.