The present study explored the applicability of two brief evidence-based interventions to improve sleep quality in inpatient psychiatry. The study involved three comparable admission wards of a psychiatric hospital. Stimulus control was introduced at the first ward, and music-assisted relaxation at the second. At the third ward, no intervention was introduced. A mixed-method study was employed. We found that nurses share the opinion that both interventions can be applied, but patients are hard to motivate. They perceived the lack of available time, busyness at the ward, and the lack of cooperation of patients as the main obstacles. The perception of a successful implementation is correlated with the perception of gained attention for sleep problems, the perception of increased care options, and the impression of effectiveness. Qualitative data showed that the effectiveness of the interventions was compromised by operational issues, commitment issues, adaptation to contextual limitations, and conflicting individual beliefs. We concluded that music-assisted relaxation is applicable in inpatient psychiatry. The application of stimulus control met with insurmountable operational issues. The nursing team is a very important factor for the implementation of evidence-based interventions at ward level. The lack of a shared urge for change and responsibility for continuity are important factors contributing to failure.