Single-port laparoscopic duodenojejunostomy employing semi-Kocherization performed for a patient with superior mesenteric artery (SMA) syndrome is presented in this report. A 24-year-old woman missed meals due to work pressure, and her body weight decreased from 42 kg to 27 kg within 6 months. After this severe weight loss, she suffered from postprandial abdominal pain. An enhanced computed tomography revealed that the aortomesenteric angle was 11° (narrow), and the distance was short at 4.5 mm. Duodenography also revealed dilatation of the proximal duodenum. These findings led to a diagnosis of SMA syndrome, and we performed single-port laparoscopic duodenojejunostomy. We first dissected the fusion between the duodenum and transverse mesocolon, such as Kocherization, enough to mobilize the duodenum; this procedure was termed semi-Kocherization. A gauze was placed in the dissected space for a landmark from the transverse mesocolon side. We confirmed the gauze at the duodenum's lateral side, then opened the transverse mesocolon, and pulled the duodenum out. We performed side-to-side duodenojejunostomy. The postoperative course was unremarkable, and she gained 4 kg within 2 months of discharge. Semi-Kocherization is shown to be an effective technique to increase duodenal mobility for performing anastomosis, and single-port laparoscopic surgery can reduce wounds and increase cosmesis.