Transition metal chalcogenides (TMCs) have great potential in diverse electrochemical technologies owing to their unique characteristics. In the present work, we portray the design and synthesis of Vanadium selenide (V2Se9)/reduced graphene oxide (rGO) forming a two-dimensional (2D) hybrid nanocomposite via a simple hydrothermal method. The successfully synthesized nanocomposite underwent in-depth surface and morphological characterizations by XRD, Raman spectroscopy, XPS, TEM, STEM and its potential as an electro catalyst was investigated by using glassy carbon electrode (GCE) for the detection of 2,4,6-trichlorophenol (TCP). The structural features favored a high charge transfer ratio, high surface area as well as excellent conductivity and catalytic activity. The V2Se9/rGO/GCE modified electrode showed a low charge transfer resistance (Rct) of 54.057 Ω cm2, a decent detection limit (LOD) of 35.07 nM and a very high sensitivity of 22 μA μM−1 cm−2 in a working range of 0.001 μM–1150 μM. This is due to the active proton interaction, surface enhancement, and positive synergistic effect between rGO and V2Se9. The proposed sensor has good detection potential in agricultural soil, river water, fish, and beverage samples like wine and apple juice. The obtained results from our investigation would elucidate the application of the catalyst in electrochemical sensors. Display omitted •Vanadium selenide (V2Se9) is prepared through facile hydrothermal process.•V2Se9 ultrasonically treated with reduced graphene oxide (rGO) forming composite.•V2Se9/rGO is used for the first time in electrochemical sensor application.•2,4,6-Trichlorophenol (TCP) detection capacity using V2Se9/rGO is 35.07 nM.•The sensor showed a high sensitivity of 22 μA μM−1 cm−2 for TCP detection.