Delirium can occur at any age, although the incidence is higher in older patients and after surgery. Although delirium is an acute, potentially reversible, cognitive disorder, there is evidence that it is associated with increased healthcare costs and imposes a significant burden on patients, families, hospitals, and public resources. The aim of this study was to investigate and assess the knowledge, behaviours, and factors influencing assessments of delirium by hospital nurses so as to predict the factors associated with their current delirium management behaviours. A cross-sectional survey was conducted among 342 nurses in different hospitals in Macau. The questionnaires included items on the respondents’ demographic information, knowledge of delirium care, nursing behaviours, and factors influencing nurses’ assessment of delirium patients in their daily practice. The descriptive statistics showed that nurses were found to have a moderate level of knowledge about the management of delirium. The repeated measures ANOVA revealed that patient factors were the most significant, outweighing individual and organizational factors as barriers to assessing patients with delirium. The Pearson’s correlation showed a moderate positive correlation between delirium care knowledge and delirium care behaviour (r = 0.339). With regard to factors influencing delirium care behaviours, multiple linear regression models showed that the significant predictors were years of work experience (β = 0.206, 95% CI: 1.125–3.158), the duration of delirium care courses (β = 0.103, 95% CI: 0.118–3.339), the knowledge of delirium care (β = 0.264, 95% CI: 0.474–1.019), and personal factors influencing nurses’ delirium assessments (β = −0.239, 95% CI: −1.031–−0.432). To enhance delirium management and achieve the optimal care of patients with delirium, formal education and training are crucial. Organizations should develop structured protocols and workflows that empower nurses. By integrating organizational strategies with individual efforts, clinical practices can be improved, resulting in optimal delirium care for patients.