The Guideline-Informed Treatment for Personality Disorders (GIT-PD) is widely used in the Netherlands and Belgium in the care of people with personality disorders. To date, no evidence existed for the possible efficacy of this treatment framework. METHOD: In an observational cohort study in four institutions, based on Routine Outcome Monitoring-data, improvements in symptom burden (BSI/OQ-45) and personality functioning (SIPP-SF) in 470 patients were examined. RESULTS: Significant improvements were observed in each of the settings for both symptom burden and personality functioning. Effect sizes for improvement in overall symptom burden ranged from d = 0.55 to 1.05. CONCLUSION: Treatment outcomes for GIT-PD are in line with treatment outcomes also seen for specialized treatments for personality disorders in similar practice studies. Possible differences between settings could be related to the intensity, structure and coherence of the GIT-PD program in question. .