The benefits of the enhanced recovery after surgery (ERAS) program to elderly patients have not been evaluated in lumbar fusion surgery. Compliance with the ERAS program is associated with prognosis. There is currently no adequate assessment about the importance of the individual components of ERAS program in lumbar fusion surgery. The aim of the study was to analyze the effect of compliance with our ERAS program and the relative importance of the individual ERAS program components among elderly patients undergoing lumbar fusion surgery. A retrospective case-review study was conducted from March 2018 to March 2020. The ERAS program for lumbar fusion surgery at our department was implemented. Overall compliance was found to be 92.9%, and this was used as a cutoff for dividing patients into higher compliance and lower compliance groups. Patient characteristics and clinical outcomes were compared between groups. The overall compliance rate was 92.9%, distributing 91 patients into the higher compliance group and 169 patients into the lower compliance group. Patients with higher compliance were younger (p=0.045). The length of stay (LOS) of patients with higher compliance was significantly shorter than that of patients with lower compliance. Patients with higher compliance had significantly fewer complications (p=0.031). A multivariate analysis showed that surgical time (p=0.029), lower compliance (p=0.034), and early oral feeding (p=0.026) were predictors of any postoperative complications. On multivariate analysis, the following items remained correlated with prolonged LOS (LOS≥12 days): older age (p=0.010), lower compliance (p<0.0001), early ambulation (p=0.018), and stick to discharge criteria (p=0.040). Low compliance with ERAS program among elderly patients undergoing lumbar fusion surgery was associated with a higher incidence of complications and prolonged LOS. The failure of early oral feeding was associated with increased complications, and the failure of early ambulation or sticking to discharge criteria was significantly more influential on prolonged LOS.