The need for belonging is a fundamental human motivation. Despite the significance of belonging, many people struggle to feel a sense of it. Healthcare organizations continue to experience workforce shortages. A workplace that does not promote belonging may prevent the career progression of its staff, leading to low morale and poor work performance. This may negatively impact their physical and mental health and compromise patient safety. The purpose was to explore inter-professional healthcare workers' sense of belonging at all levels (horizontal and vertical) and to predict possible factors that may promote/hinder it. An anonymous, descriptive, cross-sectional online electronic survey design and a modified version of the Sense of Belonging Instrument were used to collect data over 2 months in 2024 to report employees' levels of belonging. This included mental health nurses. The study was conducted at a large, urban, mental health and addiction hospital located in Ontario, Canada. A total of 441 staff members completed a questionnaire. The response rate was 24%. The variables of age, tenure, gender, ethnicity, area of work, and job satisfaction were statistically significant. Multiple regression analysis revealed that the variables of tenure, gender, employment status, and job satisfaction were predictors for belonging. Healthcare leaders must understand who feels that they belong and who does not. Every employee (regardless of their background), should feel that they belong. People should not have to feel like an outsider when they are at work. Understanding and fostering a sense of belonging in the workplace is critical to maintaining a stable workforce.