Vasopressin is a locally-injected vasoconstrictor used to reduce bleeding during gynaecological surgery. However, even in these cases, vasopressin can induce adverse effects, including bradycardia, myocardial infarction and cardiac arrest. Elevated blood concentrations of vasopressin may induce the sympathoinhibitory reflex by increasing blood pressure and augment the sympathoinhibitory reflex by activating the area postrema. In addition, pneumoperitoneum formation needed for laparoscopy as well as physiological changes caused by steep Trendelenburg positions used during robotic surgeries may cause bradycardia. Shoulder braces used to prevent slipping from a steep Trendelenburg position may also be hazardous. This case report describes a 31-year-old female patient who underwent a scheduled robotic-assisted laparoscopic myomectomy in a steep Trendelenburg position. The patient experienced a cardiac arrest 2 min after the vasopressin injection and was treated accordingly. There were no abnormal findings on the postoperative laboratory studies, chest X-ray and electrocardiogram. The patient also had clear consciousness with no other notable symptoms. The patient was discharged on postoperative day 2. The report discusses the potential adverse effects of local vasopressin injection during robotic-assisted laparoscopic myomectomy.