Emergency departments (EDs) are an important source of care for people with mental health (MH) concerns. It can be challenging to treat MH in EDs, and there is little research capturing both patient and provider perspectives of these experiences. We sought to summarize the evidence on ED care experiences for people with MH concerns in North America, from both patient and provider perspectives. Medline and EMBASE were searched using PRISMA guidelines to identify primary studies. Two reviewers conducted a qualitative assessment of included papers and inductive thematic analysis to identify common emerging themes from patient and provider perspectives. Seventeen papers were included. Thematic analysis revealed barriers and facilitators to optimal ED care, which were organized into three themes each with sub-themes: (1) interpersonal factors, including communication, patient–staff interactions, and attitudes and behaviours; (2) environmental factors, including accommodations, wait times, and restraint use; and (3) system-level factors, including discharge planning, resources and policies, and knowledge and expertise. People with MH concerns and ED healthcare providers (HCPs) share converging perspectives on improving ED connections with community resources and diverging perspectives on the interplay between system-level and interpersonal factors. Examining both perspectives simultaneously can inform improvements in ED care for people with MH concerns.