Purpose: The aim of the present study was to focus on the impact of the implementation of a person-centred approach on staff perception of the likelihood of being able to provide person-centred care and strain in the workplace. Design: The study was a controlled prospective cohort study performed at three residential care facilities in western Sweden involving all nursing staff members active from 2013 through 2015 at baseline and at three follow-ups during and after the implementation period. Two of the residential care facilities were assigned to the intervention group and one was assigned to the control group. Method: The study was designed to test the sustainability of a person-centred approach based on three aspects: partnership, narrative and documentation. A cross-section of 20 coworkers were purposively sampled from a total of 100 persons working at the two Intervention nursing homes to participate in the intervention group. The process outcome was measured as: perceived ward atmosphere, using the staff version of the validated Person-Centred Climate Questionnaire; person-centred care, measured using the validated Person-centred Care Assessment Tool; and experience of strain in work, using the Strain in Nursing Care Assessment Scale. Descriptive statistics were calculated for all variables using the SPSS Statistics software package. Findings: The results show that, at the control site, there were lower staff perceptions of the care atmosphere, higher level of strain experienced in their work and a lower likelihood of providing a person-centred care approach, whereas these factors remained rather stable over time at the intervention residential care facilities. Two contrasting results were observed—namely, that the higher the staff's perception of the likelihood of being able to provide individualised care and of a more person-centred ward atmosphere, the higher their stress levels experienced at work. In addition, older ages and long durations of work experience significantly negatively affected the staff's assessment of their ability to create an atmosphere of everydayness and to adopt a person-centred approach in care. Conclusions: The findings show that sustainability of a person-centred ward atmosphere is possible in the care of older people, despite staffing problems and other organisational challenges, according to the staff's assessment, after implementation of a person-centred programme. The more experienced staff members assessed their likelihood of being able to provide a person-centred care as lower after the implementation phase, indicating that despite the ambition of supporting person-centredness and quality of care, staffing and management difficulties that are present at the outset of the programme's implementation can later lead to stress and frustration relating to roles and routines.