Cholangiocarcinoma (CCA) is a common biliary malignancy. Despite continuing advances, novel indicators are urgently needed to identify patients with a poor prognosis. Several microRNAs (miRNAs) have been reported to be dysregulated in CCA tissues. The purpose of the current study was to explore the potential use of certain miRNAs as serum indicators. A total of 157 individuals, including103 CCA patients, were recruited into this study. We first used qRT-PCR to evaluate 5 CCA-related miRNAs in the serum of 95 individuals to identify significantly deregulated miRNAs. A logistic regression was used to analyse the potential variables influencing lymph node metastasis. Cox proportional hazards regression models were applied to determine the association between possible prognostic variables and overall survival (OS). We observed that decreased serum miR-106a confers a higher likelihood of lymph node metastasis [hazard ratio (HR) 18.3, 95% confidence interval (CI) 5.9-56.4, p < 0.01]. Additionally, lower circulating miR-106a levels (HR 5.1; 95% CI 2.2-11.8; p < 0.01) and non-radical surgery (HR 4.2; 95% CI 2.3-7.7; p < 0.01) were independent predictors for poor prognosis. Together, reduced expression of serum miR-106a is a powerful prognostic indicator for CCA patients. The dismal outcome of these CCA patients might correlate with a higher risk of lymph node metastasis.