Patient no-shows pose a significant challenge in healthcare operations, disrupting appointment schedules and affecting overall efficiency. Effectively addressing the challenge of reducing patient no-shows is crucial for outpatient service management. This study evaluates how the design of appointment systems affects patient no-show behavior. Using a difference-in-differences methodology, we analyze the effects of two appointment system update events—technical support and information provision—at a Chinese hospital. Our analysis reveals that technical support and information provision are associated with average reductions of 22.40% and 10.91%, respectively. To investigate the mechanisms behind these effects, we conduct a randomized controlled experiment with 233 participants. Our findings reveal that perceived effort and credibility mediate the relationship between information provision and patient no-shows. However, for technical support, only perceived credibility acts as a mediator. This study provides valuable insights for healthcare operations, offering design recommendations to address no-show behavior in hospital appointment systems.