Multisensory attention skills provide a crucial foundation for early cognitive, social, and language development, yet there are no fine-grained, individual difference measures of these skills appropriate for preverbal children. The Multisensory Attention Assessment Protocol (MAAP) fills this need. In a single video-based protocol requiring no language skills, the MAAP assesses individual differences in three fundamental building blocks of attention to multisensory events--the duration of attention maintenance, the accuracy of intersensory (audiovisual) matching, and the speed of shifting--for both social and nonsocial events, in the context of high and low competing visual stimulation. In Experiment 1, 2- to 5-year-old children (N = 36) received the MAAP and assessments of language and cognitive functioning. In Experiment 2 the procedure was streamlined and presented to 12-month-olds (N = 48). Both infants and children showed high levels of attention maintenance to social and nonsocial events, impaired attention maintenance and speed of shifting when competing stimulation was high, and significant intersensory matching. Children showed longer maintenance, faster shifting, and less impairment from competing stimulation than infants. In 2- to 5-year-old children, duration and accuracy were intercorrelated, showed increases with age, and predicted cognitive and language functioning. The MAAP opens the door to assessing developmental pathways between early attention patterns to audiovisual events and language, cognitive, and social development.