Purpose: The aim of this study was to explore relations between speech sound disorder severity and selective mutism in a group of children with 7q11.23 duplication syndrome (Dup7), a genetic condition predisposing children to childhood apraxia of speech (CAS) and other speech sound disorders and to anxiety disorders, including selective mutism and social anxiety disorder. Method: Forty-nine children aged 4-17 years with genetically confirmed Dup7 completed the Goldman-Fristoe Test of Articulation--Second Edition (GFTA-2), the Expressive Vocabulary Test--Second Edition (EVT-2), and the Differential Ability Scales--Second Edition (DAS-II). Parents completed the Anxiety Disorders Interview Schedule--Parent (ADIS-P). Results: Mean standard scores (SSs) were 65.67 for the GFTA-2, 92.73 for the EVT-2, and 82.69 for the DAS-II General Conceptual Ability (GCA; similar to IQ). Standard deviations for all measures were larger than for the general population. GFTA-2 SS was significantly correlated with both EVT-2 SS and DAS-II GCA. Based on the ADIS-P, 22 participants (45%) were diagnosed with selective mutism and 29 (59%) were diagnosed with social anxiety disorder. No significant differences in performance on any of the measures were found either between the group with a selective mutism diagnosis and the group that did not have selective mutism or between the group with a selective mutism and/or social anxiety disorder diagnosis and the group that did not have either disorder. Conclusions: For children with Dup7, neither the diagnosis of selective mutism nor the diagnosis of selective mutism and/or social anxiety disorder was related to severity of speech sound disorder, expressive vocabulary ability, or overall intellectual ability. Accordingly, treatment for speech sound disorder alone is unlikely to lead to remission of selective mutism or social anxiety disorder. Instead, selective mutism and/or social anxiety disorder should be treated directly. Further research is needed to determine if these findings generalize to other populations, such as children with idiopathic CAS.