Background: Patients in the emergency department are not always satisfied with the care received and the nursing care in the emergency department is sometimes described as instrumental and non-holistic. Structured quality improvement work and evidence-based practice are needed. Aim: The overall aim was to emphasize general patients in the emergency department to enhance the knowledge on how they perceive the quality of care and how the care could be improved through collaboration with the healthcare professionals. Methods: Four studies, with quantitative and qualitative designs, were conducted in a Swedish emergency department. Two hundred patients answered a questionnaire, after which 22 healthcare professionals comprising five focus groups were interviewed, and finally 200 patients were included in an intervention study. Results: The following five areas for improvement were identified: “information, respect and empathy”, “pain relief”, “nutrition”, “waiting time” and “general atmosphere”. Of these areas, the healthcare professionals prioritized “information, respect and empathy”, “waiting time” and “pain relief” to be highlighted in the quality improvement work. Although goals and suggestions for changes were stated, barriers to quality improvement at different levels in the health care were detected. The results of the intervention study showed that structured nursing assessment of the patients’ abdominal status and nurse-initiated intravenous opioid analgesic could increase frequency of analgesic and reduce time to analgesic in the emergency department. Patients perceived lower pain intensity and improved quality of care in pain management. Conclusions: An uncomplicated nursing intervention, related to pain management, based on the results from a patient questionnaire and interviews with healthcare professionals, can improve the care process and pain management in the emergency department, as well as patients’ perceptions of the quality of care in pain management. To succeed with continuous quality improvement work, barriers to change should be addressed.