Background <p>This study aimed to evaluate the efficacy of a biodegradable membrane composed of polycaprolactone (PCL) and polyglycolic acid (PGA) for guided bone regeneration in bone defects.</p> Methods <p>Twelve Wistar albino rats were initially included in the study. During follow-up, 3 rats were excluded. To maintain the planned sample size, these animals were replaced with 3 additional rats. Consequently, a total of 15 rats were used, and the final statistical analyses were based on 12 rats. Twenty-four standardized bilateral parietal bone defects were created and randomly allocated to four groups. Defects received either 3D-printed PCL membranes or PCL membranes coated on the inner surface with PGA (PCL/PGA). Control defects received PCL membranes alone. Group 1 received PCL/PGA with a human-derived freeze-dried bone graft, an equine xenograft, and autologous blood. Group 2 received PCL/PGA with autologous blood. Group 3 received PCL with autologous blood. Six rats were euthanized at 4 weeks and six at 8 weeks. Histopathological and stereological analyses were performed to assess newly formed bone volume.</p> Results <p>At week 4, Group 2 showed significantly greater newly formed bone volume and total tissue volume than all other groups (<i>p</i> &lt; 0.001). At week 8, newly formed bone volume in Group 2 remained significantly greater than in Groups 1 and 3 (<i>p</i> &lt; 0.001) but did not differ from the control group (<i>p</i> &gt; 0.05).</p> Conclusion <p>In this GBR model, the PGA-coated PCL membrane enhanced new bone formation during the early phase of bone regeneration.</p>