Mental Health Nurse Consultants are advanced practice mental health nurses who consult with nurses and other health professionals in a general hospital setting. The aim of this review was to analyse and synthesize the available evidence related to the impact of Mental Health Nurse Consultants on the care of general hospital patients experiencing concurrent mental health conditions. The integrative literature review method was utilized as it allows for the inclusion and integration of quantitative, qualitative, and mixed methods research which produces a synthesized understanding of data to inform practice, policy, and research. The Preferred Reporting Items of Systematic Review and Meta-Analyses guided the search strategy. All published studies examining the impact of clinical consultations provided by Mental Health Nurse Consultants on the mental health care of general hospital patients were included. The 19 selected articles were from North America, Australia, the United Kingdom, and Europe. Fifteen were quantitative, three were qualitative, and one used mixed methods. The findings highlight the role is generally positively received by hospital staff. The results indicate that clinical consultations provided by Mental Health Nurse Consultants (i) may improve patient experiences of mental health conditions, (ii) influence aspects of care delivery, (iii) are valued by staff, particularly nurses, and (iv) increase staff competence and confidence in the provision of mental health care. The review highlighted significant limitations of the available evidence, the need for contemporary discussion and debate of MHNC theory and practice, and further evaluation of the role to inform future service delivery.