Current amplification-based microRNA (miRNA) detection approaches are limited by the small sizes of miRNAs as well as amplification bias/artifacts. Herein, we report on an amplification-free miRNA assay based on elevated affinity interaction between polyadenylated miRNA and bare gold electrode. The poly(A) extension on the 3′ ends of magnetically isolated miRNA targets facilitated high adsorption efficiency onto gold electrode surfaces for electrochemical detection without any cumbersome electrode surface functionalization procedures. The assay showed excellent detection sensitivity (10 fM) and specificity and was demonstrated for quantitative miR-107 detection in human cancer cell lines and clinical urine samples. We believe our assay could be useful as an amplification-free alternative for miRNA detection.