AbstractThe abnormal expression of a microRNA (miRNA) is associated with many major diseases. Therefore, the stability, reliability, and sensitivity of miRNA detection are of paramount importance for early diagnosis and therapeutics. Field‐effect transistor (FET) devices, as sensors, have many advantages, including their multiparameter accessibility and ease of large‐scale manufacturing, but the electrical signals of most FETs are vulnerable in humid environments over extended periods of time, further limiting their sensing capability and performance. In this paper, sophisticated all‐graphene‐based field‐effect transistors (AG‐FETs) are designed and fabricated by means of the covalent layer‐by‐layer (LBL) assembly of graphene oxide (GO), with the electrical capability of FETs and the intrinsic properties of graphene being incorporated in a single device. Thanks to the covalent configuration and the fluorescence quenching properties of graphene, the AG‐FETs possess great electrical stability and outstanding solution resistibility and could detect miRNA sensitively, stably, and reliably through electrical and fluorescence dual signals, which mostly avoid false positives during the test process. This is done without the use of any amplification techniques and even in real samples. These dual‐signal biosensors with excellent performance have promising potential for application in early clinical diagnoses and biomedical research.