In a changing context, the use of knowledge management (KM) generates value and a long-lasting competitive advantage. As a critical issue for societal development, sustainable organisations must consider the relationship between KM and healthcare. They must investigate how knowledge is created and identify potential predictors of knowledge-sharing behaviour to support a hospital’s long-term knowledge-management strategy. Managers could benefit from KM strategies to improve the performance of hospitals and other healthcare organisations. This study aimed to determine the knowledge management and sustainability performance of a hospital organisation based on the perspective of the healthcare managers. A cross-sectional research approach was employed involving the healthcare managers of a government-subsidised hospital in the Hail Region of Saudi Arabia. The study was conducted between September and October 2022. The results demonstrated that knowledge management was commendable (4.41 ± 0.470) and had high sustainability performance (4.28 ± 0.558). Predictors for knowledge management included gender (B = 0.201; p = 0.002), managerial position (B = 0.285; p < 0.000), years of experiences as manager (B = 0.319; p < 0.000) and educational attainment (B = 0.092; p = 0.003). The predictors for sustainability were gender (B = 0.023; p < 0.000), managerial position (B = 0.352; p < 0.000) and years of experience as a manager (B = 0.0648; p < 0000). The study found that knowledge management was a predictive factor in sustainability regarding economic (B = 0.735; p < 0.000), social (B = 1.028; p < 0.000), environmental (B = 0.774; p < 0.000), technical (B = 0.751; p < 0.000) and governance (B = 0.526; p < 0.000), while knowledge management had a strong correlation to sustainability performance (R = 0.663; p < 0.000). Therefore, knowledge management for learning should be consistently created and shared to keep members involved in the core of operations. When knowledge is put into practice, it can help an organisation innovate, sustain better performance and guarantee long-term success. These study findings may additionally persuade workers to put more effort into knowledge management.