The development of flexible electrodes is of considerable current interest because of the increasing demand for modern electronics, portable medical products, and compact devices. We report a new type of flexible electrochemical sensor fabricated by integrating graphene and MoS2 nanosheets. A highly flexible and free-standing conductive MoS2 nanosheets/reduced graphene oxide (MoS2/rGO) paper was prepared by a two-step process: vacuum filtration and chemical reduction treatment. The MoS2/graphene oxide (MoS2/GO) paper obtained by a simple filtration method was transformed into MoS2/rGO paper after a chemical reduction process. The obtained MoS2/rGO paper was characterized by scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy. The electrochemical behavior of folic acid (FA) on MoS2/rGO paper electrode was investigated by cyclic voltammetry and amperometry. Electrochemical experiments indicated that flexible MoS2/rGO composite paper electrode exhibited excellent electrocatalytic activity toward the FA, which can be attributed to excellent electrical conductivity and high specific surface area of the MoS2/rGO paper. The resulting biosensor showed highly sensitive amperometric response to FA with a wide linear range.