Background Angelman syndrome is a rare disorder in which most individuals do not develop speech. Testing of communication ability using traditional neuropsychological measures reveals a performance level at or near the floor of the instrument resulting in an inability to detect change when experimental therapeutics are applied. Methods Nine individuals, with molecularly confirmed AS, ranging in age from 34 to 126 months, and a single healthy control child (age 16 months) were audio and video‐recorded while interacting with a licensed speech‐language pathologist in an attempt to elicit vocalization and non‐verbal communication. Thirty‐minute audio recordings were transcribed and categorized per the Stark Assessment of Early Vocal Development‐Revised and a phonetic inventory was created. Using video recordings, gestures were classified by function, either behavioral regulation or social interaction and further categorized as deictic or representational (i.e., behavioral regulation) and joint attention or shared engagement (i.e., social interaction). Results The range of vocalizations produced by the children with AS was characteristic of children between 0–6 months and none of the children with AS used advanced forms of vocalizations. The mean frequency of reflexive vocalizations, control of phonation and expansion far exceeded the number of uses of canonical syllables, consistant with the characteristics of children around 12 months of age. Most vocalizations were either laughter or isolated vowels, only three children with AS produced consonant‐vowel combinations. Children with AS tended to use central and low vowels with few producing high vowels, suggesting the presence of childhood apraxia of speech. Conclusion Our results show the utilization of video‐recorded behavioral observations provides a feasible and reliable alternative for quantification of communication ability in this patient population and may be employed during future clinical studies of potential therapeutics.