An increasing number of Americans are experiencing sleep problems. There is evidence of a complex, bidirectional relationship between sleep disorders, substance abuse, and mental health symptoms. Institutional settings have been shown to elicit sleep problems as well. This pilot study was conducted with 28 patients in private, residential, dual-diagnosis treatment for addiction and mental health disorders. Upon admission, consenting patients were administered the Addiction Severity Index to assess pretreatment substance use and mental health symptoms. Patients followed a normal course of treatment as well as participated in a nightly sleep hygiene group that included relaxation suggestions. Evaluations with the Addiction Severity Index were completed again 30 days after discharge from treatment. Significant improvements in some substance use patterns as well as mental health symptoms were noted. Although results cannot be directly attributed to the use of a sleep hygiene group, this pilot study lays the foundation for future investigations of interventions supporting sleep in the dual-diagnosis population.