Purpose The purpose of this paper is to identify the factors that explain the acceptance of self-service ordering systems (SOSs) for restaurants and to explore the effects of “self-service system service quality” (SSQ) and “interpersonal service quality” (ISQ) on the acceptance factors extended from the Unified Theory of Acceptance and Use of Technology model. Design/methodology/approach This study targets customers who have recently used SOSs to order foods in middle-class restaurants. In total, 402 valid survey samples were obtained. Partial least squares (PLS) analysis was used to examine the factors of user acceptance of using SOSs. Findings The results of the PLS-SEM analysis indicate that SSQ has a significant effect on accuracy expectancy, speed expectancy and effort expectancy; ISQ has a significant effect on accuracy expectancy, speed expectancy, effort expectancy and facilitating conditions; and accuracy expectancy, speed expectancy, effort expectancy, social influence, facilitating conditions and budget expectancy significantly influence user acceptance of SOSs. Furthermore, user experiences moderate the effect of speed expectancy and effort expectancy on user acceptance. Originality/value This study introduces three technology acceptance factors (accuracy, speed and budget) for researchers to consider in the future. It also extends the knowledge about the human service factor when middle-class restaurants adopt self-service technologies (SSTs). Recommendations are provided for system developers to improve the system quality of SSTs and service staff to rethink their roles in adopting SSTs in the service industry.