BACKGROUND: An intervention project was conducted in three nursing home wards in Sweden. Most patients had severe dementia. The intervention consisted of supervision for individualized and documented nursing care, based on multidimensional assessment. AIM: To illuminate changes in carers' approach after the intervention. METHODS: Several data collections were conducted across the intervention and consisted of nursing documentation, patient life stories as told by carers, video recorded interactions, stimulated recall interviews and a questionnaire. Both quantitative and qualitative methods were used in the analyses. FINDINGS: The findings from the different methods mirrored each other and added to the credibility of the intervention. Communicated knowledge about patients improved in nursing documentation and also as told by carers. Carers were differently skilled in managing the complexity of nursing care situations before as well as after the intervention, but the intervention contributed to developing carers in 'confirming nursing care'. They also improved in their ability to verbalize reflections about their everyday life with patients with dementia. CONCLUSION: Supervision made it possible for carers to share their lived experiences about their day-to-day life with patients, which could promote personal and professional development and thus improve care quality. It also appeared that a detailed assessment tool used as part of the nursing process contributed to seeing a patient as a real person behind a dementia surface.