The high frequency of complicated forms of gastric cancer in young and middle-aged patients is associated with faster and more biologically aggressive tumor growth, as well as with a delay in diagnosis. The study aimed to evaluate the efficacy, safety, and technical feasibility of surgical interventions for complicated forms of gastric cancer in young and middle-aged patients. We studied 98 patients with complicated forms of gastric cancer from IIB to stage IV according to the TNM8 classification with a predominant lesion of the antrum and body of the stomach. We performed open, laparoscopic, or robot-assisted surgeries of various scopes (R0 or R1), mostly gastrectomy and subtotal distal resection of the stomach. We compared the clinical manifestations of the disease, the time of surgery, intraoperative blood loss, postoperative complications, survival, and quality of life in 2 groups of patients divided by age: 19 young patients (mean age 39.4±4.4 years) and 79 middle-aged patients (mean age 53.9±5.8 years). Clinical manifestations of gastric cancer were more pronounced in young patients. The number of postoperative complications in patients of Group 2 was significantly higher (7.8% to 5.26%) compared to Group 1 (p<0.05). Rehabilitation in patients who underwent laparoscopic surgery was significantly (p<0.05) faster than with the traditional method. The overall survival of young patients with IIB-IV stages of gastric cancer was 0.8 months less, and among patients with III-IV stages it was 2.4 months less than in the group of middle-aged patients and did not depend on the surgery scope. There were no statistically significant differences between the groups in terms of intraoperative blood loss, duration of surgery and hospital stay. Increased surgery duration of in middle-aged patients significantly correlated with the number of postoperative complications. Extended surgeries do not significantly increase the number of lethal, life-threatening complications. Combined surgeries in the R0 scope in patients with advanced gastric cancer (including with carcinomatosis) improved the quality of life of patients yet did not increase in overall survival, which determines the reasonable limits of surgical aggression.