UNLABELLED: The ability to reduce stuttering in everyday speaking situations is the core component of the management plan of many who stutter. However, the ability to maintain the benefits of speech-restructuring treatment is known to be compromised, with only around a third of clients achieving this [Craig, A. R., & Hancock, K. (1995). Self-reported factors related to relapse following treatment for stuttering. Australian Journal of Human Communication Disorders, 23, 48-60; Martin, R. (1981). Introduction and perspective: Review of published research. In E. Boberg (Ed.), Maintenance of fluency. New York: Elsevier]. The aim of this study was to determine whether the presence of mental health disorders contributes to this failure to maintain fluency after treatment. Assessments for mental health disorders were conducted with 64 adults seeking speech-restructuring treatment for their stuttering. Stuttering frequency, self-rated stuttering severity and self-reported avoidance were measured before treatment, immediately after treatment and 6 months after treatment. Stuttering frequency and situation avoidance were significantly worse for those participants who had been identified as having mental health disorders. The only subgroup that maintained the benefits of the treatment for 6 months was the third of the participants without a mental health disorder. These results suggest that prognosis for the ability to maintain fluency after speech restructuring should be guarded for clients with mental health disorders. Further research is needed to determine the benefits of treating such disorders prior to, or in combination with, speech-restructuring. EDUCATIONAL OBJECTIVES: The reader will (1) evaluate the impact of one or more mental health disorders on medium-term outcomes from speech-restructuring treatment for stuttering, (2) describe how this finding affects prognosis for certain groups of stuttering clients, (3) evaluate how these finding are consistent with estimates of post-treatment relapse after speech-restructuring treatment, (4) describe two test instruments for detecting mental health disorders, and (5) outline the findings about the relation between pre-treatment stuttering severity and mental health disorders.