Aim: To investigate barriers to healthcare professionals recognizing and managing delirium in hospitalized older people. Design: A mixed-methods systematic review. PROSPERO ID: CRD42020187932. Data Sources: MEDLINE, EMBASE, PsycINFO and CINAHL were searched (2007 to February 2023). Review Methods: Included studies focused on healthcare professionals' recognition and management of delirium for patients aged 65 years and over in a hospital ward or emergency department. Enhancing rigour, screening of results was conducted independently by two researchers. Qualitative and quantitative data were tabulated separately and grouped. Data were compared to identify similarities and differences. All studies were quality appraised. Results: 43 studies were included; 24 quantitative, 16 qualitative and three mixed-methods. Data synthesis highlighted synergy between qualitative and quantitative findings. Barriers were reflected in six themes: (1) healthcare professionals' knowledge and understanding; (2) communication; (3) workforce development; (4) interprofessional working; (5) confounders; and (6) organizational constraints. Conclusions: Of significance, for older adults in hospital experiencing delirium, there is variability in whether and how well it is recognized and managed. To prevent adverse outcomes best practice guidance for screening, recognizing, diagnosing and managing delirium in older people needs to be agreed and disseminated widely. Supporting healthcare professionals to care for this patient population using an integrated approach is essential, how to involve and communicate with patients and their family and friends, how to recognize and manage delirium for patients with additional needs, e.g., those living with dementia and/or a learning disability. Hospitals need to have policy and guidance in place for the recognition and management of delirium in older adults presenting to a ward or to an emergency department. An IT infrastructure is needed that integrates assessments and care management plans in patient electronic records and makes them accessible within and across teams in hospital, primary and community care settings. Patient or Public Contribution: There was no patient or public contribution to this systematic review. Implications for the Profession and Patient Care: Healthcare professionals can be better supported to be able to recognize and manage delirium during an acute hospital stay for older adults. This includes maximizing best care for those patients living with dementia, involving families and friends to help understand patients' baseline status and changes and supporting families and friends during this process. Of significance, attention to hospital IT infrastructures is warranted, integrating screening, assessment and care management plans in patients' electronic records and making these accessible to healthcare professionals caring for this patient population across care settings. Impact: What problem did the study address? Delirium is a common condition experienced by older hospitalized patients, but it is consistently under-recognized which has implications for patient and organization outcomes. To help address this, understanding barriers to healthcare professionals recognizing and managing delirium for this patient population is paramount. What were the main findings? Barriers to healthcare professionals recognizing and managing delirium for this patient population were synthesized in six themes: (1) healthcare professionals' knowledge and understanding, (2) communication; (3) workforce development; (4) interprofessional working; (5) confounders; and (6) organizational constraints. Where and on whom will the research have an impact? The findings of this original systematic review can contribute to hospital policy and protocol for the recognition and management of delirium in older patients. The findings can meaningfully contribute to workforce professional development for practitioners caring for older people during an acute hospital stay and for practitioners in primary and community settings involved in the follow-up of patients post hospital discharge. For researchers, the findings indicate several research recommendations including investigating the impact of an education programme for nurses and other healthcare professionals on the recognition and management of the condition and understanding and investigating how best to support delirium-related distress experienced by patients and their families and practitioners. Reporting Method: This systematic review was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (Page et al., 2021).