Background <p>This study evaluated whether the dynamic change in total bilirubin (TBIL) after percutaneous transhepatic cholangiographic drainage (PTCD) was associated with major postoperative complications and 90-day mortality in patients with hilar cholangiocarcinoma (HCCA).</p> Methods <p>We retrospectively analyzed 173 patients with HCCA who underwent PTCD before curative-intent resection at three Chinese centers. The bilirubin reduction rate (BRR) was defined as the difference between the TBIL level measured one day before PTCD and that measured one day before surgery, divided by the interval between measurements. Logistic regression was used for major complications, and Firth’s penalized logistic regression was used for 90-day postoperative mortality. Receiver operating characteristic analysis assessed the discriminatory performance of BRR for major complications.</p> Results <p>Major complications occurred in 64 patients (37.0%), and 8 patients (4.6%) died within 90&#xa0;days after surgery. On multivariable analysis, BRR (OR = 0.86, 95% CI 0.79–0.95, <i>p</i> = 0.002) and intraoperative transfusion (OR = 2.04, 95% CI 1.06–3.92, <i>p</i> = 0.033) were independently associated with major complications. Lower platelet count (OR = 0.99, 95% CI 0.97–1.00, <i>p</i> = 0.013) and lower albumin (OR = 0.80, 95% CI 0.65–0.99, <i>p</i> = 0.042) remained independently associated with 90-day postoperative mortality. BRR showed modest discriminatory ability for major complications (AUC = 0.644, 95% CI 0.563–0.726). Using the optimal cutoff value (4.863&#xa0;μmol/L·day⁻¹), the high-BRR group had lower rates of major complications and 90-day mortality than the low-BRR group.</p> Conclusions <p>BRR after PTCD was independently associated with major complications after HCCA resection, but its modest discriminatory performance supports its use only as an adjunctive marker.</p>