Rabies is a serious zoonotic disease in almost all warm-blooded animals and causes fatal encephalitis. The detection of rabies virus (RABV) is critical and remains a significant challenge. Herein, an electrochemiluminescence resonance energy transfer (ECL-RET) and electrochemical (EC) dual-mode immunosensor was developed for highly sensitive detection of RABV glycoprotein. Dendritic mesoporous silica nanoparticles (DMSNs) were employed to load Ru(bpy)32+ and to obtain ECL probes (Ru@DMSNs). Ru@DMSNs were decorated on the electrode surface, followed by the modification of the RABV antibody (Ab1). RABV was specifically recognized and captured by Ab1, causing the decline of the ECL signal due to the obstruction of electron transfer. Additionally, manganese oxide nanoparticles (MnOx) modified with Ab2 can further quench the ECL signal of Ru@DMSNs via the RET between Ru@DMSNs and MnOx. Meanwhile, MnOx can catalyze the oxidation of o-phenylenediamine (o-PD), generating a significant differential pulse voltammetry (DPV) signal as a second signal to monitor RABV glycoprotein concentration. Consequently, an immunosensor was developed to achieve dual-signal detection of RABV and improve reliability. Under the optimal conditions, detection ranges of 0.10 pg·mL-1 to 10 ng·mL-1 for ECL (with an 88 fg·mL-1 detection limit) and 1 pg·mL-1 to 2 ng·mL-1 for EC (with a 0.1 pg·mL-1 detection limit) were obtained for RABV detection. The reliability of this immunoassay was validated by eight brain tissue samples. The results were found to be compatible with the results of the real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, indicating the potential applicability of this method for RABV diagnosis.