A novel 3D-printed biodegradable cage composed of polycaprolactone (PCL) and beta-tricalcium phosphate (β-TCP) in a mass ratio of 50:50, with stable resorption patterns and mechanical strength has been developed for lumbar interbody fusion. This is a prospective cohort study to evaluate the short- and mid-term safety and efficacy of this biodegradable cage in posterior lumbar interbody fusion (PLIF) surgery. This was a prospective single-arm pilot clinical trial in 22 patients with a follow-up time of 1, 3, 6, and 12 months, postoperatively. Clinical outcomes were assessed using the Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and Visual analogue scale (VAS) for leg pain and low back pain. Radiological examination included X-ray, CT scan, and three-dimensional reconstruction to evaluate surgical indications, intervertebral space height (ISH), intervertebral bone fusion and cage degradation. A total of 22 patients was included, with an average age of 53.5 years. Among 22 patients, one patient lost to follow-up and one patient withdrew from the clinical trial because of cage retropulsion. The remaining 20 patients showed significant improvement in clinical and imaging outcomes compared to the preoperative period. The overall mean VAS for back decreased from 5.85 ± 0.99 preoperatively to 1.15 ± 0.86 at the 12-month follow-up (p < .001); the VAS for leg decreased from 5.75 ± 1.11 to 1.05 ± 0.76 (p < .001); the JOA score improved from 13.8 ± 2.64 to 26.45 ± 2.46 (p < .001). The mean intervertebral space height (ISH) increased from 11.01 ± 1.75 mm preoperatively to 12.67 ± 1.89 mm at the 12-month follow-up and the bone fusion reached 95.2% (20/21 disc segments). Partial resorption (inferior to 50% compared with the initial cage size) were found in all cages (21/21). The clinical and radiological assessments showed that the application of 3D-printed biodegradable PCL/β-TCP cages in PLIF yielded satisfactory results at the 12-month follow-up. In the future, long-term clinical observations and controlled clinical trials are required to further validate the safety and efficacy of this novel cage.