Background: The home literacy environment (HLE) has rarely been examined for individuals with neurodevelopmental disorders, including individuals with Williams syndrome and Down syndrome. Method: The current study surveyed carers of individuals with Down syndrome (n = 48) and Williams syndrome (n = 18) in the United Kingdom (UK). Results: The study reports that individuals with Down syndrome were rated higher in general reading skills and writing, while the Williams syndrome group scored higher for speaking. Yet, individuals with Down syndrome were more likely to engage in informal activities than instructional activities and the frequency of informal activities related to reading outcomes for those with Down syndrome but not Williams syndrome. Additionally, this study reports that age was not related to the HLE for both groups. Conclusion: This is the first study to report on the HLE of individuals with Williams syndrome and supports the key role of the HLE in the development of literacy skills for individuals with Williams syndrome and Down syndrome.