Williams syndrome (WS), a rare genetically based neurodevelopmental disorder, is characterized by gait abnormalities that resemble basal ganglia-parkinsonian deficits in the internal regulation of stride length. In the current study, we explored whether visual or attentional cues would improve gait function in adults with WS, when compared to adults with Down syndrome (DS) and neurologically normal controls. The spatiotemporal characteristics of gait were measured using the GAITRite walkway while participants walked with visual cues set at 20% greater than preferred stride length (externally cued), or with an attentional strategy of maintaining the stride length without the assistance of visual cues (internally cued). Although the WS and DS groups were able to achieve the criterion and normalize stride length in both conditions, the WS group significantly reduced their gait speed and cadence in the externally cued condition when compared to controls. In the internally cued condition, the WS group also showed reduced speed and increased intra-individual variability in speed and stride time. These findings suggest that the primary deficit is not one of difficulty regulating stride length in WS, but rather indicates more widespread dysfunction within visuomotor regions.