A combination of fluoropyrimidines and platinum is widely accepted as the standard first-line treatment for advanced gastric and gastroesophageal adenocarcinomas. However, the benefit compared with platinum-free chemotherapeutic regimens remains controversial. We compared the efficacy and safety of capecitabine with oxaliplatin or docetaxel, as first-line therapy in advanced gastric cancer. Eligible patients were randomly assigned to receive either capecitabine and oxaliplatin (XELOX) (capecitabine 1,000 mg/m2; twice daily for 14 days with oxaliplatin 130 mg/m2 on day 1, every 21 days), or DX (capecitabine 1,000 mg/m2; twice daily for 14 days with docetaxel 75 mg/m2 on day 1, every 21 days). The primary endpoint was the objective response rate (ORR). Secondary endpoints included the disease control rate (DCR), progression-free survival, overall survival, and prespecified safety endpoints. Ninety patients were enrolled in the West China Hospital from April 2012 to August 2016; a total of 83 and 66 patients were eligible for safety and efficacy analyses, respectively. Between the XELOX and DX groups, ORR (24.2% vs 24.2%, p = 1.000), DCR (90.9% vs 75.8%, p = 0.099), progression-free survival (6.1m vs 4.1m, p = 0.346), and overall survival (8.8m vs 9.0m, p = 0.973) were similar. There was no significant difference in toxicity between the two regimens. The frequent grade 3 or higher toxicities in the XELOX and DX groups were peripheral neuropathy and hematological toxicity, respectively. Toxicity was tolerable; no treatment-related deaths occurred in either group. The DX regimen was not superior to XELOX, but instead, similar. The platinum-containing regimen remains the preferred first-line option for advanced gastric and gastroesophageal adenocarcinomas, and DX might be considered as an alternative for patients unsuitable for platinum-containing chemotherapy. Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.