Background and Aims Preoperative sarcopenia is a syndrome characterized by reduced skeletal muscle mass and strength, and it is associated with various adverse postoperative outcomes. Gastric cancer patients may experience transient or persistent postoperative cognitive dysfunction (POCD), which significantly impacts their quality of life and prognosis. However, it remains unclear whether this complication is linked to sarcopenia. Therefore, this study was conducted to investigate further the impact of preoperative sarcopenia on postoperative complications and long-term outcomes in patients undergoing radical gastric cancer surgery, with a particular focus on the relationship between sarcopenia and POCD, in order to provide insights for preoperative assessment and postoperative management of gastric cancer patients.Methods The clinical data of gastric cancer patients who underwent radical surgery in the Third Department of Surgery at the Fourth Hospital of Hebei Medical University between January 2014 and January 2015 were retrospectively collected. Patients were divided into the sarcopenia and non-sarcopenia groups based on preoperative L3 skeletal muscle index, handgrip strength, and gait speed measurements. The clinicopathologic characteristics of sarcopenic patients, as well as the impact of sarcopenia on short-term clinical outcomes and long-term prognosis, were analyzed. Additionally, factors influencing the development of POCD were determined.Results A total of 320 gastric cancer patients were included, of whom 59 (18.44%) were diagnosed with sarcopenia. Compared with the non-sarcopenia group, sarcopenic patients had significantly lower bady mass index, serum total protein, serum albumin, and hemoglobin levels, with a higher proportion of patients aged ≥60 years, NRS 2002 score ≥3, comorbid pulmonary disease, and those undergoing open surgery (all P<0.05). After balancing the baseline characteristics of the two groups using propensity score matching (PSM), each group included 59 patients. The analysis revealed that the overall incidence of postoperative complications was higher in the sarcopenia group than in the non-sarcopenia group (54.24% vs. 32.20%, P=0.016). The sarcopenia group also had a significantly higher incidence of Clavien-Dindo grade Ⅱ-Ⅳ complications and postoperative infectious complications (27.12% vs. 5.08%, P=0.001; 33.90% vs. 15.25%, P=0.019). The average hospital stay was significantly longer for sarcopenic patients (12.54±4.7 d vs. 7.68±3.8 d, P=0.005). Additionally, the 5-year overall survival (OS) and disease-free survival (DFS) rates were lower in the sarcopenia group compared to the non-sarcopenia group (both P<0.05). Cox multivariate analysis showed that sarcopenia, tumor pT stage, and tumor pN stage were independent risk factors for 5-year OS and DFS. At the same time, adjuvant chemotherapy was a protective factor for prognosis (all P<0.05). Among the 118 patients after PSM, 34 (28.81%) were diagnosed with POCD. Logistic multivariate regression analysis indicated that preoperative sarcopenia, the number of preoperative comorbidities, and anesthesia duration of ≥2 h were independent risk factors for POCD, while intraoperative use of dexmedetomidine was a protective factor (all P<0.05).Conclusion Preoperative sarcopenia is closely associated with unfavorable postoperative outcomes and the development of POCD in patients undergoing radical gastric cancer surgery. Clinicians should emphasize the detection of sarcopenia during preoperative evaluation and implement proactive interventions and postoperative management strategies to improve clinical outcomes and long-term survival rates.