Hydrogen peroxide (HO) is a signaling molecule that has the capacity to control a variety of biological processes in organisms. Cancer cells release more HO during abnormal tumor growth. There has been a considerable amount of interest in utilizing HO as a biomarker for the diagnosis of cancer tissue. In this study, an electrochemical sensor for HO was constructed based on 3D reduced graphene oxide (rGO), MXene (TiC), and multi-walled carbon nanotubes (MWCNTs) composite. Three-dimensional (3D) rGO-TiC-MWCNTs sensor showed good linearity for HO in the ranges of 1-60 μM and 60 μM-9.77 mM at a working potential of -0.25 V, with sensitivities of 235.2 µA mM cm and 103.8 µA mM cm, respectively, and a detection limit of 0.3 µM (S/N = 3). The sensor exhibited long-term stability, good repeatability, and outstanding immunity to interference. In addition, the modified electrode was employed to detect real-time HO release from cancer cells and cancer tissue ex vivo.