OBJECTIVES: National Health Service (NHS) values, such as empathy and therapeutic optimism, are integral when supporting service users with complex mental health presentations. There is some evidence to suggest that psychological formulation can increase empathy and optimism in healthcare professionals. This study, therefore, aimed to investigate whether a psychological formulation of a hypothetical service user with a complex presentation, typically labelled with a diagnosis of borderline personality disorder (BPD), increased empathy and therapeutic optimism in professionals working in mental health inpatient services. Sixty-six mental health professionals working in NHS inpatient services took part in a pre- and post-vignette study. Participants were asked to read a case vignette about a hypothetical service user, with a diagnostic label of BPD, and complete questionnaires capturing levels of empathy and therapeutic optimism. Participants were then randomized into two conditions and either asked to read the same information again (control condition) or read a psychological formulation based on the same hypothetical service user (intervention condition). The findings were analysed using a series of ANCOVAs/ANCOHETs. Two constructs of empathy (i.e. perspective taking and empathic concern), and therapeutic optimism significantly increased following exposure to the psychological formulation when compared to the control group condition. This study warrants further replication. These initial findings; however, indicate that psychological formulation can significantly increase the ability to perspective take, display empathic concern, and hold therapeutic optimism towards service users with a presentation associated with a diagnosis of BPD.