Purpose <p>The clinical relevance of the red blood cell distribution width (RDW) in patients with distal cholangiocarcinoma (DCC) undergoing pancreaticoduodenectomy (PD) has not been clearly investigated.</p> Methods <p>The relationship between the preoperatively measured RDW and prognosis for the recurrence/survival was evaluated in patients with DCC undergoing PD. A subgroup analysis was also performed in patients with pathological stage I DCC.</p> Results <p>A total of 77 patients were included in the analysis. The cutoff value of the preoperatively measured RDW was set at 14%, and the normal reference range at our center was ≤ 14%. The patient group with an RDW &gt; 14% (<i>n</i> = 30) had a significantly lower mean serum albumin level, higher mean serum carbohydrate antigen 19–9 level, and a higher proportion of cases with pathological lymphatic invasion and showed a significantly worse overall survival than the patient group with an RDW ≤ 14% (<i>n</i> = 47). Similar findings were noted in both the overall study population and patients with pathological stage I disease. Multivariate analysis identified an RDW &gt; 14% and pathological lymph node metastasis as independent risk factors for a poor postoperative survival.</p> Conclusion <p>The preoperatively measured RDW is a promising prognostic predictor in patients with DCC undergoing PD.</p>