Background: In this study, the focus is on how to support the competence development needed for nursing assistants in home care. Home care services for older persons can be challenging concerning the nature of the interpersonal interaction and communication needed to care for and respond to the diverse needs of older people who seek to live well in our communities. This implies a need to offer more person-centred care (PCC) to older persons. However, there is a lack of knowledge on how to develop such competence. We, therefore, developed A Person-centred CommunicaTION (ACTION) programme, which is a web-based educational intervention aimed at supporting competence development for nursing assistants. The research objective is to evaluate the ACTION programme with respect to participants’ responses to and the effect of the intervention. Methods: A multicentre case–control study with pre- and post-assessments was designed. The ACTION programme will be implemented at home care units, in two different geographic areas in Sweden. A total of 300 nursing assistants will be recruited: 150 for the intervention group and 150 for the control group. We will evaluate the impact measures and the process. Pre- and post-assessments will be performed with data collected via a) audio recordings of communication, b) a questionnaire on self-efficacy communication skills, PCC, empathy and job satisfaction, c) user data, evaluation forms, field notes and observations, and d) interviews. The data will be analysed with descriptive and analytic statistics and/or qualitative methods for meanings. Discussion: This study has the potential to contribute to the evidence supporting competence development required to offer person-centred and quality home care to older persons and to meet upcoming needs for flexible and easily accessible competence development. Trial registration: ISRCTN64890826. Registered 10 January 2022, https://www.isrctn.com/ISRCTN64890826