This article describes a pilot study that was carried out to in order to gain an indication as to whether mental healthcare nurses can apply evidence-based interventions for sleep problems effectively in inpatient mental health care. The study had a pre-test/post-test design and a comparison group was used. The study was performed on three psychiatric admission wards, located in three different towns in one province of The Netherlands. The participants were inpatients (18-60 years old) admitted owing to severe mental health problems like psychotic, mood or anxiety disorders. Of the newly admitted patients, 62.8% perceived having a sleep problem. Two brief, evidence-based interventions were introduced on two of the wards: the first with stimulus control (SC) as active component; the second with music-assisted relaxation (MAR). A third ward, with no interventions other than usual care, served as a point of comparison. Sleep quality was monitored using the Richards-Campbell Sleep Questionnaire (RCSQ). The change score means of the treatment groups were compared with the mean score of the comparison group by means of a t-test. Estimates of effect were calculated. The results of this study showed that MAR produced a statistically significant improvement of sleep quality and showed a large effect size. The total RCSQ score did not improve significantly. SC failed to produce statistically significant improvement of sleep quality, nor of the RCSQ total score. This pilot study provided a strong indication that mental health nurses can apply MAR effectively. No such indication was found for stimulus control.