Background: Although many studies using whole-exome sequencing or targeted sequencing have reported the molecular profile of BTC, its clinical implications remains unclear. In this study, we assessed a predictive role of DDR gene mutations in advanced BTC patients treated with platinum-containing regimen. Methods: Eighty-eight patients with pathologically-confirmed BTC who received first-line gemcitabine-cisplatin combination (n = 69) or fluoropyrimidine-oxaliplatin combination (n = 19) were included in this analysis. Targeted exome sequencing was performed using Foundation Medicine T7 assay or in-house OncoPanel AMC. Germline or somatic mutations in ATM, ATR, BAP1, BARD1, BRCA1, BRCA2, BRIP1, CHEK2, FAM175A, GEN1, MLH1, MSH2, MSH6, MRE11A, NBN, PALB2, PMS2, RAD50, RAD51, RAD51C, RAD51D, and XRCC2 were classified as DDR gene mutations. Data regarding baseline characteristics and treatment outcomes were retrospectively obtained from medical records. Results: The median age was 62 years (range, 25-78), with male comprising 64.8% (n = 57). By primary tumor site, 21 patients with GBC (23.9%), 44 with ICC (50.0%) and 23 with ECC (26.1%) were included. Most patients received palliative chemotherapy for their initially metastatic (50.0%) or recurred (44.3%) disease; the rest 5.7% had locally advanced disease. The median PFS and OS of overall patients were 7.1 and 16.1 months, respectively with median follow-up duration of 20.2 months. DDR gene mutations were found in 63.5% of patients. BRCA2 (18.2%) was most frequently mutated, followed by ATM (13.6%), and ATR (8.0%). DDR gene mutations were significantly associated with prolonged PFS (presence vs. absence; median, 6.9 vs. 5.7 months; P = 0.013) and OS (median, 21.0 vs. 13.3 months, P = 0.009). The impact of DDR gene mutations remained significant in multivariate analyses for PFS that included other prognostic factors (hazard ratio, 0.51; P = 0.009), but not for OS. Conclusions: The presence of DDR gene mutations might be a promising predictive biomarker for response to platinum-based chemotherapies in advanced BTC. Future investigation using novel agents targeting DDR gene alteration in BTC are warranted.