Background: Surgery for gastric cancer may result in free intraperitoneal cancer cells. This study aimed to determine whether laparoscopic gastrectomy with complete mesogastric excision (D2+CME) reduces the number of free intraperitoneal cancer cells. Methods: Patients with gastric cancer who had a conventional D2 or D2+CME laparoscopic distal gastrectomy between April 2015 and February 2017 were included in the study. Intraoperative peritoneal washings were collected before and after tumour resection. Reverse transcriptase-quantitative real-time PCR for carcinoembryonic antigen (CEA) was used to assess the presence of gastric cancer cells. Results: Eighty-five patients underwent conventional D2 lymphadenectomy and 76 had the D2+CME procedure. Of 161 peritoneal fluid samples obtained before gastrectomy, 137 (D2, 72; D2+CME, 65) had low CEA expression indicative of no cancer cells. After gastrectomy, high CEA expression was detected in 23 of the 72 samples (32 per cent) from patients in the D2 group, and in ten of the 65 samples (15 per cent) from the D2+CME group. In the overall cohort, mean CEA expression level after gastrectomy was lower in the D2+CME group than in the D2 group (P=00038). In patients with low CEA expression before gastrectomy, disease-free survival in the D2+CME group was better than that in the D2 group (P=0033). Conclusion: Laparoscopic distal gastrectomy with complete mesogastric excision reduces the number of free intraperitoneal cancer cells and is associated with a better disease-free survival than conventional D2 gastrectomy.