The prognosis of metastatic gastric cancer (GC) is poor, with a median survival time of less than a year. Capecitabine is a prodrug, metabolized by thymidine phosphorylase to its cytotoxic metabolite (5-FU). Few studies have compared capecitabine and 5-FU in mGC. In this retrospective study, we compared the efficacy and safety of modified DCF (mDCF) (docetaxel, cisplatin, and 5-FU) and modified DCX (mDCX) (docetaxel, cisplatin, and capecitabine) regimens for first-line treatment in patients with mGC. The study included 112 mGC patients treated with either mDCF (n = 69) or mDCX (n = 43) between 2010 and 2021. Demographic data, response rate, progression-free survival (PFS), overall survival (OS), and adverse events were evaluated. The complete response rate in the mDCF group was 10.1%, whereas the complete response rate in the mDCX group was 2.3%. The partial response rate for mDCF and mDCX were 29% and 37%, respectively. The 2 treatment arms of the study had the same objective rate of response and disease control rate (DCR). PFS and OS rates were comparable between the 2 groups. The median PFS in the mDCF and mDCX arms were 6.0 months (95% CI, 4.87–7.14) and 5.0 months (95% CI, 4.10–5.90) respectively (P = .08). The median OS in the mDCF and mDCX arms were 9.0 months (95% CI, 7.53–10.47) and 9.0 months (95% CI, 6.87–11.11) respectively (P = .07). Neutropenia, asthenia, stomatitis, and nausea/vomiting were the most frequently reported grade 3 to 4 adverse events (AEs). The rates of grade 3/4 AEs and dose reduction were comparable between the 2 groups. There was no treatment discontinuation due to grade 3 to 4 AE. As a first-line treatment for patients with mGC, mDCX and mDCF regimens have comparable efficacy and tolerability profiles.