Emergency department (ED) staff are often the first point of contact for individuals in suicidal crisis. Despite this, there is no published research systematically examining the factors influencing decision-making for this patient group. MedLine, CINAHL, PsycINFO, Web of Science and Cochrane Library databases were searched for three key concepts: (1) suicide, (2) accident and emergency department and (3) decision-making. Three reviewers screened titles, abstracts and full papers independently against the eligibility criteria. Data synthesis was achieved by extracting and analyzing study characteristics and findings. The Mixed Methods Appraisal Tool (MMAT) was used to assess the quality of included studies. Seventeen studies met the eligibility criteria and were included in this systematic review. Studies were published from 2004 to 2020 and were of good methodological quality. A number of patient (method of self-harm, age, gender), contextual (availability of services and staff) and staff-related factors (attitudes, training, knowledge) were reported to influence decision-making for patients in suicidal crisis presenting to EDs. Decision-making in the ED is complex and is influenced by patient, contextual and staff-related factors. These decisions can have an impact on the future care and clinical pathways of patients in suicidal crisis. Additional training is needed for ED staff specifically related to suicide prevention.