Historically, dualistic healthcare systems have resulted in limited mental healthcare provision within physical health settings, with service users reporting poor care specifically while attending emergency departments (EDs) in a mental health crisis. Modern approaches to healthcare recognize these inequalities and are moving towards integrating healthcare systems that allow more holistic and seamless experiences for service users. This mixed-method review examines the experiences and perceptions of service users attending EDs for a mental health crisis. Systematic searches of eight databases on two platforms (EBSCO, OVID) and grey literature databases (Open Grey, Base) were conducted. Studies were systematically screened for inclusion based on predetermined eligibility criteria and quality assessed using the Mixed Methods Appraisal Tool. Findings were tabulated and synthesized using thematic synthesis. Ten studies consisting of qualitative and mixed-method designs were included in the review. Five overarching themes emerged from the synthesis: social constructs, service provider, service provision, effectiveness, and emotional impact. The findings from this review show that service users continue to have negative experiences in EDs due to stigmatizing attitudes and low skill in managing mental health needs, whereas more positive experiences are attributed to the availability of mental health liaison services. Tackling stigma, improving communication and staff training, providing calm environments, and addressing structural issues that promote better interagency working and reduce gaps in services are needed to improve mental health service user experience. Future research should focus on trauma-informed approaches in EDs to improve person-centred care for service users experiencing a mental health crisis.