Purpose: With the current study, we aimed to reveal the similarities and differences in sensory profiles between Williams syndrome (WS) and autism spectrum disorder. Methods: Using the sensory profile questionnaire completed by the caregivers, we analyzed the WS (n = 60, 3.4-19.8 years) and autistic (n = 39, 4.2-14.0 years) groups. Results: The Severity Analysis revealed a significant group difference in Sensory Sensitivity but not in Low Registration, Sensation Seeking, and Sensation Avoiding subscales. Age can modulate the subscale scores differently across groups. For Sensation Seeking, the scores of both groups decreased with development. However, the scores of Sensory Sensitivity decreased with age in the autistic group but not in the WS group. Sensation Avoiding scores increased with development in the WS group but not in the autistic group. No significant developmental changes were observed in Low Registration. Conclusion: This study highlights the cross-syndrome similarities and differences in sensory profiles and developmental changes in autistic individuals and individuals with WS.