Purpose: Atypicalities in the prosodic aspects of speech are commonly considered in clinical assessments of autism. While there is an increasing number of studies using objective measures to assess prosodic deficits, such studies have primarily focused on the intonational and rhythmic aspects of prosody. Little is known about prosodic deficits that are reflected at the segmental level, despite the strong connection between prosody and segmental realization. This study examines the nature of sibilant-vowel coarticulation among male adult native speakers of Cantonese with autism and those without. Methods: Fifteen Cantonese-speaking autistic (ASD) adults (mean age = 25 years) and 23 neuro-typical (NT) adults (mean age = 20 years) participated. Each participant read aloud 42 syllables with a sibilant onset in carrier phrase. Spectral means and variance, skewness and kurtosis were measured, and regressed by vocalic rounding (rounded vs. unrounded), cohort (ASD vs. NT), sibilant duration, and articulation rate. Results: While neurotypical participants exhibit sibilant-vowel coarticulation that are sensitive to variation in sibilant duration, autistic participants show no sensitivity to segmental temporal changes. Conclusion: These findings point to the potential for atypicalities in prosody-segment interaction as an important characteristic of autistic speech.