Overwhelming workloads for mental health nurses (MHNs) can result in psychological problems like depression, anxiety, and burnout. This study assesses the impact of workload on the psychological well-being of MHN. The study investigated the relationship between workload and psychological well-being among MHNs. An integrative review design was adopted, and a search was conducted in the databases PubMed, Web of Science, and CINAHL from June 26 to August 15 to identify primary articles investigating the relationship between psychological well-being and the workload of hospital-based MHNs. The search included both quantitative and qualitative studies. Seven (7) studies (5 quantitative, 2 qualitative) were reviewed following the screening of 123 studies retrieved from the search across the databases. Studies have revealed that MHNs face psychological threats from high job demands and aggressive patient behaviour. A large-scale study is needed to establish a causal relationship between workload and psychological stress among MHNs.