The number of emergency department (ED) visits has markedly increased in Taiwanese hospitals in recent years. The associated income of ED visits often accounts for more than half of the annual income of a hospital. Therefore, customer satisfaction with healthcare services provided in emergency departments has become a vital indicator of hospital operation. The survey was carried out from September 2011 to March 2015. The research tool was developed based on the Taiwan Healthcare Indicator Series (THIS), and is divided into five parts consisting of 50 questions. A total of 795 customer satisfaction questionnaires were included in this survey. The survey discussed the trends of ED customer satisfaction from 2011 to 2015 and proposed five variables of satisfaction and their correlations. ED customer satisfaction levels in 2012, 2014, and 2015 were above the overall mean score. Gender, age, educational level, place of residence, department visited, and time period of the visit to the ED influenced hospital facilities, waiting time of patients, staff’s attitude, medical processes and consequences of service, which were all variables of customer satisfaction. From the 5-year trend curve, medical procedures and consequences of service had positive impacts on customer satisfaction and consequences of service showed a stronger influence than medical procedures. Moreover, manpower deployment was also regarded as an influential indicator of satisfaction