This study aimed to examine the association of serum microRNAs (miRNAs) with diagnosis and growth of abdominal aortic aneurysm (AAA), and to test their diagnostic and prognostic value.The expression levels of 800 miRNA tags were assessed in 108 AAA patients and 12 age- and sex-matched healthy controls (HC) and 12 patients with peripheral artery disease (PAD) using nanoString Technologies. Findings were assessed in an independent sample of 66 AAA patients and 29 age and sex-matched HC by reverse transcriptase PCR (rtPCR). AAA growth was assessed by a median of 3 (Interquartile range (IQR) 2, 3) repeat ultrasound scans over a median follow up of 1.1 (IQR 1.0, 2.0) years. The association of the miRNA with AAA diagnosis and growth were examined by regression and linear mixed effects analyses. The diagnostic and prognostic potential of the miRNAs were examined using area under the receiver operator characteristic curve (AUC), net reclassification index (NRI) and Cox hazard analyses.In comparison to HC, a model combining clinical risk factors, let-7b-5p and miR-548n had an AUC of 98.0% (95% CI 95.6, 100.0; p=.003) for diagnosing AAA, which was a significant improvement over clinical risk factors alone (NRI: 1.74; 95% CI 1.61, 1.87; p0.001). In comparison to PAD, a model combining clinical risk factors and miR-548n had an AUC of 99.6% (95% CI 98.9, 100.0, p=.037) for diagnosing AAA, which was a significant improvement over clinical risk factors alone (NRI 1.79, 95% CI 1.68, 1.91; p0.001). In the longitudinal cohort, none of the miRNA were able to predict the likelihood of reaching surgical threshold diameter better than clinical risk factors alone.Serum let-7b-5p and miR548n significantly improved ability to diagnose AAA. None of the miRNAs had independent prognosis value in predicting AAA growth.