Purpose: This study examined the effects of an intensive voice treatment Lee Silverman Voice Treatment (LSVT LOUD) on children with Down syndrome (DS) and motor speech disorders. Method: A Phase I, multiple baseline, single-subject design with replication across nine participants with DS was used. Single-word intelligibility, acoustic measures of vocal functioning, and parent perceptions of pre- and posttreatment communication function were used as treatment outcome measures. Results: All participants completed the full dose of LSVT LOUD and showed gains on one or more of the outcome measures. Patterns of posttreatment improvements were not consistent across participants but were more frequently observed on trained maximum performance tasks compared to tasks reflecting generalization of the treatment skillset. Some participants exhibited a stronger response to treatment, whereas others showed a mixed or weaker response. Parents liked the treatment protocol, perceived benefits from intensive intervention, and indicated they would strongly recommend LSVT LOUD to other parents who have children with DS and motor speech disorders. Conclusions: These preliminary results show that children with DS tolerated intensive voice treatment without adverse effects and made select meaningful therapeutic gains. The treatment evidence from this study warrants Phase II treatment studies using LSVT LOUD with a larger group of children with DS.