Purpose Comprehensive geriatric assessment (CGA) is a widely used approach in geriatric care and involves multidisciplinary assessments focused on determining a frail elderly persons medical, psychological and functional capability to develop an integrated plan for treatment. The purpose of this paper is to describe and scrutinize the CGA implementation process at six acute geriatric departments in three county councils and to study the outcome by the documentation in the patient medical records, and the staff perceptions using CGA. Design/methodology/approach The paper describes the implementation process stages. Outcome measures were based on patient medical records reviews at baseline and follow-ups at year 1 and year 2. Staff perceptions of using CGA were gathered by a questionnaire at the second follow-up. Findings The implementation had not yet reached sustainability so the implementation process must continue. Results show that documentation on the different areas increased in year 1, as well as the use of standardized assessment tools. However, results from the reviews for year 2 showed some decrease. Staff considered CGA to have high value for the geriatric patient but pointed out the need for continuing education. Originality/value Successful strategies for this implementation were strong support from the managers, small seminars, CGA rounds, good introduction routines for new staff and the use of reminders such as pocket-sized focus cards. A high staff turnover occurred during the study, which probably had a significant negative impact on the results.