Objective To investigate the effect of an educational intervention of nursing staff on change in psychotropic use and related costs among older long-term care residents. Design A secondary analysis of a randomized controlled intervention study with 12 months of follow-up. Setting Assisted living facilities in Helsinki, Finland. Subjects Older (≥65 years) residents ( N = 227) living in assisted living facility wards ( N = 20) in Helsinki in 2011. Intervention The wards were randomized into two groups. In one group, the nursing staff received training on appropriate medication therapy and guidance to recognize potentially harmful medications and adverse effects (intervention group); in the other group, the nursing staff did not receive any additional training (control group). Main outcome measures Change of psychotropic use counted as relative proportions of WHO ATC-defined daily doses (rDDDs) among older long-term care residents. In addition, the change in drug costs was considered. Comparable assessments were performed at 0, 6, and 12 months. Results A significant decrease in both rDDDs and the cost of psychotropics was observed in the intervention group at 6 months follow-up. However, at 12 months, the difference between the intervention and control group had diminished. Conclusions Educational training can be effective in reducing the doses and costs of psychotropics. Further studies are warranted to investigate whether long-term effects can also be achieved by various educational interventions. Registration number ACTRN 12611001078943 KEY POINTS We explored the effect of staff training on psychotropic use and associated costs among older long-term care residents. Educational training of nursing staff was beneficial as regards the actual drug doses of psychotropics, and cost savings in psychotropic medication were achieved. Educational training was efficient in the short-term, but further research is warranted to achieve long-term effects.