Background: Trastuzumab in combination with platinum-based chemotherapy is the standard first line regimen in HER2 positive advanced gastric cancer. However, there is no data concerning continuation of trastuzumab beyond first line progression. Methods: This retrospective multicenter study include all consecutive patients with HER2 + advanced gastric or gastro-esophageal junction (GEJ) adenocarcinoma who received after progression of trastuzumab plus platinum-based chemotherapy, a second line chemotherapy with irinotecan, taxane or platinum salt, with or without trastuzumab. The prognostic variables with P values ≤0.10 in univariate analysis were eligible for the Cox multivariable regression model. Results: From August 2007 to March 2015, 104 patients were included (median age, 60.8 years; male, 78.8%; PS 0-1, 71.2%) with advanced (metastatic : 99%) gastric (45.2%) or GEJ (54.8%) cancer. All patients had received first line treatment based on trastuzumab plus fluoropyrimidine and cisplatin (n=54; 51.9%) or oxaliplatin (n=50; 48.1%). As second line chemotherapy, 67 patients (64.4%) received FOLFIRI regimen, including 19 who have continued trastuzumab; 23 patients (22.1%) received a taxane regimen (paclitaxel or docetaxel), including 12 with trastuzumab; and 14 patients (13.5%) received a platinum-based chemotherapy (different from that used in first-line), including 8 with trastuzumab. When considering all regimens of second-line chemotherapy, continuation (n=39) versus discontinuation (n=65) of trastuzumab was significantly associated with an increase on PFS (4.4 vs 2.3 months; p=0.002) and OS (12.6 vs 6.1 months; p=0.001). In multivariate Cox model (including ECOG PS, tumor grade, number of metastatic site, and second-line treatment), continuation of trastuzumab was significantly associated with longer PFS (HR=0.56; 95%CI [0.35-0.89]; p=0.01) and OS (HR=0.47; 95%CI [0.28-0.79]; p=0.004). Conclusions: This study suggests that maintenance of trastuzumab plus second line chemotherapy beyond disease progression has clinical benefit in patients with HER2 positive advanced gastric cancer. These results deserve a prospective randomized validation.