Children with Autism Spectrum Disorder (ASD) often experience delayed speech development. Current research shows that ASD is associated with atypical vocal quality. An early sign of ASD is difficulty recognizing and using speech prosody, which is how a speaker manipulates changes in pitch, loudness, and duration to emphasize what is important. Pitch is the perceptual representation of fundamental frequency (f0), or the physical speed by which the vocal folds vibrate (cycles per second). Manipulating f0 is a developmental skill that neurotypical children learn in infancy. Children with ASD struggle with this skill. This study examined whether quantifiable differences in pitch exist among three groups of children: (1) children diagnosed with ASD, (2) children with developmental delay (DD) but not ASD, and (3) neurotypical children. Children from each group were audio-recorded individually in a naturalistic setting. For each child, the f0 of each utterance was first identified, and then analyzed quantitatively (e.g., mean, range, and other descriptive statistics) and visually (i.e., the f0 pitch contour or shape). The values were then compared across the three groups. Children with ASD tended to have higher f0 means and medians than the other groups. However, results did not support a hypothesis that children with ASD showed less manipulation of f0, only that their utterances were primarily non-word productions. Fundamental frequency is a critical acoustic vocal parameter and is important in understanding speech development. Identifying differences in f0 between children with ASD and without ASD can help expand the knowledge base of Autism diagnostic teams and early interventionists. This knowledge will enable professionals and caregivers to develop more efficient strategies for supporting communicative development in children with ASD.