Background Laparoscopic surgery has been widely accepted to treat early-stage gastric cancer. However, it is still controversial to perform laparoscopic gastrectomy plus D2 lymphadenectomy for locally advanced gastric cancer. We performed the present study to compare the long-term outcomes of patients after laparoscopic or open gastrectomy plus D2 lymphadenectomy. Methods The clinicopathological data of 182 gastric cancer patients receiving gastrectomy plus D2 lymphadenectomy between January 2011 and December 2015 at Shenzhen Traditional Chinese Medicine Hospital were retrospectively retrieved. The overall survival (OS) and disease-free survival (DFS) of these 182 patients were compared. Then, the prognostic significance of positive lymph node ratio (LNR) was assessed. Results As a whole, OS (P = 0.789) and DFS (P = 0.672) of patients receiving laparoscopic gastrectomy plus D2 lymphadenectomy were not significantly different from those of patients receiving open surgery. For stage I patients, laparoscopic gastrectomy plus D2 lymphadenectomy was not significantly different from open surgery in terms of OS (P = 0.573) and DFS (P = 0.157). Similarly, for stage II patients, laparoscopic gastrectomy plus D2 lymphadenectomy was not significantly different from open surgery in terms of OS (P = 0.567) and DFS (P = 0.830). For stage III patients, laparoscopic gastrectomy plus D2 lymphadenectomy was not significantly different from open surgery in terms of OS (P = 0.773) and DFS (P = 0.404). Laparoscopic or open gastrectomy plus D2 lymphadenectomy was not proven by Cox regression analysis to be an independent prognostic factor for OS and DFS. High LNR was significantly associated with worse OS (P < 0.001) and DFS (P < 0.001). Surgical type did not significantly affect prognosis of patients with low LNR or survival of patients with high LNR. Conclusions For patients with gastric cancer, laparoscopic gastrectomy plus D2 lymphadenectomy was not inferior to open surgery in terms of long-term outcomes. LNR is a useful prognostic marker for GC patients.