To identify the risk factors associated with prolonged length of stay (LOS) despite an enhanced recovery after surgery (ERAS) protocol in short-level lumbar fusion surgery.We gathered data for all patients undergoing short-level lumbar fusion surgery from January to November 2021. Given the discharge criteria, a threshold was set according to mean LOS, and two groups were spontaneously formed: LOS shorter than the threshold for discharge (control group, n = 114) and LOS longer or equal to the threshold for discharge (delayed group, n = 72). Preoperative metrics were compared to identify risk factors associated with prolonged LOS.A total consecutive 186 patients with complete medical records were enrolled (77 males and 109 females; mean age 71.08 ± 5.70 years). After dichotomization according to the threshold for discharge, there were 114 patients in control group and 72 in delayed group. Statistical analysis demonstrated that age ≥75 years (P = .002), female sex (P < .001), American Society of Anesthesiologists grade ≥ 3 (P = .035), operation time (P < .001), anesthesia time (P < .001), ambulation time >1 day (P = .027), removal of urinary catheter time >1 day (P = .019), fusion levels (P < .001), Clavien-Dindo grade > 1 (P <.001) and allogeneic transfusion (P = .009) were significantly related to prolonged LOS. Binary logistic regression revealed that age (odds ratio (OR) 5.149; 95% confidence interval (CI) 2.045-12.966, P = .001), sex (OR 5.185, 95% CI 2.183-12.317, P < .001) and Clavien-Dindo grade > 1(OR 15.936, 95% CI 5.220-48.652, P < .001) were independent risk factors of prolonged LOS.In this retrospective study, we analyzed the potential risk factors associated with delayed LOS despite implementing ERAS, further, binary logistic regression exhibited that age ≥75 years old, female sex and Clavien-Dindo grade >1 were independently correlated with prolonged LOS.© The Author(s) 2022.