Introduction Currently, the standard treatment for gastric and gastroesophageal junction (GEJ) adenocarcinoma, including distal esophagus, consists of perioperative chemotherapy (CT) according to FLOT schedule (5FU/leucovorin/oxaliplatin and docetaxel), or of concomitant chemoradiotherapy (CTRT) based on CROSS regimen. However, due to the relatively lack of direct comparisons between perioperative CT and neoadjuvant CTRT, the effectiveness of these new combinations is unknown. Therefore, we performed a network meta-analysis (NMA) to compare the efficacy of different neoadjuvant treatments for gastric and GEJ adenocarcinoma in terms of overall and disease-free survival (OS and DFS). Materials and methods We searched MEDLINE, Embase, and Cochrane from database inception until February 1st 2022 for randomized clinical trials that enrolled adults with gastric and GEJ carcinomas and provided data about OS and/or DFS. Between-group comparisons were estimated using hazard ratios (HRs) with 95% credible intervals (95% CrIs). Surface under the cumulative rank (SUCRA) curve plots were produced. The primary outcome was OS, secondary endpoint DFS. Results A total of 1247 citations were screened; 14 randomized clinical trials were included. In Bayesian comparisons, FLOT-based CT ranked as one of the better regimens with a probability of 41%, both with induction CT followed by CTRT ( P  = 0.45). For DFS analysis, the FLOT regimen was the preferred option ( P  = 0.62). Conclusions In conclusion, this NMA adds further evidence to the optimization of treatment strategies for gastric and GEJ adenocarcinomas and confirms that incorporation of perioperative triplet-based CT improved both OS and DFS compared to surgery alone and other preoperative strategies.