Oblique lumbar interbody fusion (OLIF) is a minimally invasive lateral lumbar fusion technique and patients are discharged 1–2 days after surgery. Because OLIF utilizes a retroperitoneal approach close to the superior hypogastric plexus, postoperative urinary retention (POUR) may not be an uncommon problem. The purpose of this study was to present the incidence and outcomes of POUR with a systematic care protocol. The records of 102 consecutive patients (M:F = 34:68; mean age, 68.0 ± 8.4 years) were retrospectively reviewed. After OLIF, the indwelling urinary catheter was immediately removed, and every patient was encouraged to void within 6 hours. The POUR care protocol, following a clinical pathway, was based on residual urine (RU), which was monitored with an ultrasound bladder scan after each voiding or every 6 hours for 48 hours. The incidence rate of POUR was 44% (45/102) at 24 hours, 17% (17/102) at 48 hours, and 2% (2/102) at 1 month. Preoperative urological symptoms (odds ratio [OR], 3.6) and violation of the protocol (OR, 28.0) were risk factors at 24 hours. At 48 hours, violation of the protocol was the only risk factor (OR, 10.5). Identifying risk factors and a preemptive care protocol may reduce permanent POUR.