OBJECTIVES: Constant observation is used in hospitals with people with dementia to manage their safety. However, opportunities for proactive care are not consistently recognised or utilised. A systematic review of constant observation was conducted to understand measures of effectiveness and facilitators for person-centred approaches. METHOD: Electronic databases were searched between 2010 and 2022. Four reviewers completed screening, quality assessments and data extraction with 20% checked for consistency. Findings were presented through narrative synthesis (PROSPERO registration CRD42020221078). FINDINGS: Twenty-four studies were included. Non-registered staff without specific training were the main providers of constant observation. Assessments and processes clarifying the level of observation encouraged reviews that linked initiation and discontinuation to a patient's changing needs. Examples of person-centred care, derived from studies of volunteers or staff employed to provide activities, demonstrated meaningful engagement could reassure a person and improve their mood. Proactive approaches that anticipated distress were thought to reduce behaviours that carried a risk of harm but supporting evidence was lacking. CONCLUSION: Non-registered staff are limited by organisational efforts to reduce risk, leading to a focus on containment. Trained staff who are supported during constant observation can connect with patients, provide comfort and potentially reduce behaviours that carry a risk of harm.