A 64-year-old female patient with locally-advanced breast cancer in her left breast was referred to my outpatient department for implantable port catheter insertion. The procedure was performed smoothly, but a post-operation chest X-ray showed a rare type of implantable port catheter tip malposition, in which the catheter formed a circular loop near the port hub. A week later, the patient had problems with getting her blood drawn and drug injection. She returned to my outpatient department, and revision surgery was performed to correct the malfunction of the catheter. Given the rarity of such an outcome, we present this case and report the possible causes and its management.