Objective: To evaluate the long-term outcomes and prognostic factors of locally advanced gastric cancer with serosa-invasion. Methods: This study is a retrospective cohort study. The clinical and pathological data of 495 patients with locally advanced gastric cancer with serosa-invasion who underwent laparoscopic radical gastrectomy in Department of General Surgery, the First Hospital Affiliated to Army Medical University from October 2012 to October 2018 was analyzed retrospectively. There were 356 males and 139 females with an age (M(IQR)) of 59 (16) years (range: 18 to 75 years). Observation indicators included postoperative results and long-term prognosis. The survival curve was drawn by the Kaplan-Meier method. Univariate and multivariate prognostic analysis was performed using the Cox proportional hazards model. Results: Among the 495 patients, a total of 57 patients (11.5%) were lost to follow-up, with a follow-up time of 89 (40) months (range: 23 to 134 months). The 5-year disease-free survival rate (DFS) and the 5-year overall survival rate (OS) were 56.0% and 58.2%, respectively. The 5-year DFS for patients with stage ⅡB, ⅢA, ⅢB, ⅢC were 71.2%, 60.5%, 51.6%, 33.3%, respectively. The 5-year OS for patients with stage ⅡB, ⅢA, ⅢB, ⅢC were 71.2%, 62.2%, 54.1%, 39.3%, respectively. Multivariate analysis showed that age >65 years (DFS: HR=1.402, 95%CI: 1.022 to 1.922, P=0.036; OS: HR=1.461, 95%CI: 1.057 to 2.019, P=0.022), lymph node dissection number less than 25 (DFS: HR=1.348, 95%CI: 1.019 to 1.779, P=0.036; OS: HR=1.376, 95%CI: 1.035 to 1.825, P=0.028), pathological stage Ⅲ (DFS: HR=2.131, 95%CI: 1.444 to 3.144, P<0.01; OS: HR=2.079, 95%CI: 1.406 to 3.074, P<0.01), and no postoperative chemotherapy (DFS: HR=3.127, 95%CI: 2.377 to 4.113, P<0.01; OS: HR=3.768, 95%CI: 2.828 to 5.020, P<0.01) were independent prognostic factors for the decrease in DFS and OS rates. Conclusions: Laparoscopic radical gastrectomy for locally advanced gastric cancer with serosa-invasion could achieve satisfactory long-term oncological outcomes. More lymph node dissection and standardized postoperative adjuvant chemotherapy are expected to further improve the prognosis of patients with locally advanced gastric cancer with serous invasion after laparoscopic radical surgery.