Individuals living with mental illness can experience dire oral health and face numerous barriers to oral health care. While mental health providers are important in oral health promotion, there is a major gap in knowledge on their oral health knowledge, attitudes and practices and guidelines/recommendations for best practice. This integrative review addresses this gap by synthesising evidence on mental health providers oral health knowledge, attitudes and practices and available clinical guidelines/recommendations. Searches were undertaken across six databases, supplemented with grey literature searches. The inclusion criteria were mental health providers, including nurses, doctors and allied health providers. Articles or guidelines/recommendations were excluded if they primarily related to drug and alcohol or substance use and eating disorders. A total of 16 studies and five guidelines/recommendations were included (20 were of high-moderate quality). Mental health providers were receptive to playing a role in oral health promotion and screening and this was supported by guidelines/recommendations. However, current practices of mental health providers in promoting oral health are fragmented and inconsistent due to various barriers: limited knowledge, education, and training, lack of collaboration with dental services, heavy workloads, time constraints and challenging client behaviours. This review highlights an urgent need to strengthen supports for mental health providers to promote oral health with professional development in oral health, more detailed clinical practice guidelines, brief and user-friendly oral health screening tools and streamlined dental referral pathways.