In the rituximab era, the optimal treatment modality for primary gastric diffuse large B-cell lymphoma (PG-DLBCL) still remains unclear. We performed a retrospective, multicenter analysis of 65 patients with PG-DLBCL to assess the efficacy and toxicity of the addition of rituximab to conventional chemotherapy. When compared with conventional chemotherapy, there was a trend that rituximab plus chemotherapy yielded a higher complete response rate, 5-year event-free survival (EFS) rate and 5-year overall survival (OS) rate, but this was not statistically significant. In subgroup analysis, better OS was observed only for patients with advanced-stage disease when rituximab was added. When involved-field radiotherapy (IFRT) was included, EFS and OS were significantly prolonged in the conventional chemotherapy group, but not in the immunochemotherapy group. If focusing on patients with localized-stage disease receiving immunochemotherapy, the efficacies of short-course rituximab (R)-chemotherapy plus IFRT and 6-8 courses of R-chemotherapy without IFRT were comparable. In conclusion, it is necessary to carry out prospective randomized trials to help further illuminate the role of rituximab in the PG-DLBCL treatment landscape. If a patient has been treated with a non-rituximab-containing regimen, additional IFRT should be considered, and for patients with advanced-stage disease, rituximab should be considered.