Introduction Small tumors may be difficult to identify visually and require preoperative effort to locate. Recent advancements in mixed reality technology have improved surgical accuracy in various departments. Here, we present the application of mixed reality‐assisted surgery and a guiding marker in the case of small retroperitoneal metastasis of uterine cancer. Case presentation A 67‐year‐old female with a history of uterine cancer had a retroperitoneal metastasis in the lateroconal fascia near the right diaphragm, measuring 2 cm and infiltrating the peritoneum. We performed precise surgical planning using the preoperative mixed reality software “Holoeyes” on a head‐mounted display called HoloLens2. Novel techniques, including ultrasonography‐guided placement of a guiding marker and strategic port‐site placement facilitated by HoloLens2, ensured accurate tumor identification and laparoscopic resection with minimal blood loss and no intraoperative complications. Conclusion The use of mixed reality‐assisted surgery and a guiding marker effectively enhanced the precision of retroperitoneal tumor resection.