In mental health, oral health is often given little attention. Mental health nurses (MHNs) are professionally the appropriate target group to support maintaining and increasing oral health. We aimed to develop and validate personas that reflect the attitudes and needs of MHNs regarding oral health in patients with a psychotic disorder. We used a human-centered design with contextual interviews (n = 10) to address the key issues of the problems and needs of MHNs working with patients with a psychotic disorder. We analyzed the data thematically and reflected on insights into unique personas, which were then validated by conducting semi-structured interviews (n = 19) and member checking. Four personas were found based on attitudes and perspectives, barriers, needs, suggestions for interventions, and site conditions regarding practicing oral care in this patient group. Our findings were as follows: the attitudes and perspectives differed from not feeling any responsibility to a holistic obligation, including oral health; suggestions for interventions for MHNs ranged from interventions focusing on improving skills and knowledge to using practical tools; most MHNs recognized themselves within a persona that had a holistic obligation that included oral health; in addition, the MHNs indicated that they considered the issue of oral health in this patient group important, but, in practice, took little responsibility for that role. These findings suggest that a toolkit with interventions for MHNs that are tailored to the personas that emerged from our research should be developed by MHNs in co-creation with designers. The differences between the perceived role and MHNs’ practice in oral health highlighted the need for role clarification and professional leadership of MHNs regarding oral health, which should be considered when developing interventions.