In this study, the effective usage of PAMAM dendrimer was implemented for detection of microRNA-34a (miRNA-34a) which was known as a biomarker for many vital diseases such as cancer, Alzheimer, etc. The microscopic and electrochemical characterization of the PAMAM modified electrode surface was performed successively. The experimental conditions such as DNA probe, target concentration, hybridization time were optimized for the purpose of effective nucleic acid hybridization between miRNA-34a RNA target and its complementary DNA probe. Under optimum conditions, the selectivity of the impedimetric nucleic acid biosensor was tested in the presence of microRNA-15a (miRNA-15a) and microRNA-660 (miRNA-660). Our impedimetric biosensor platform could be selectively detect its target, miRNA-34a even if the hybridization was done in fetal bovine serum (FBS), which served a complex media for detection process. This disposable, easy-to-use, cheap and time saving impedimetric biosensor platform is the first study in the literature on behalf of electrochemical detection of miRNA-34a.