Herein we reported graphene (Gr) was firstly fabricated on glassy carbon electrode (GCE) by drop casting method, subsequently  polyaniline (PAN) and Palladium (Pd) nanocomposite were fabricated by two-step electrochemical depositing process on graphene dispersed glassy carbon electrode (Gr/GCE) and used as an electrochemical sensor for determination of Tetrachlorvinphos (TCP < /span>) pesticide in vegetables. Here most of the work has been focused on the preparation and characterization of modified electrode with cyclic voltammetry (CV) and scanning electron microscopy (SEM). The modified composite electrode unveiled significantly good voltammetric response on TCP. Square wave voltammetry (SWV) was used for determination of TCP at optimized conditions such as square wave frequency, step potential, pH of buffer, applied sample volume, accumulation potential and accumulation time. The well-defined reduction (C=C) peaks were acquired over the potential maximum around at -1.3V in acidic medium in Briton-Robinson (B-R) buffer solution at low current values. The low current peaks were obtained over the concentration of TCP at 1.5×10 -6  M with lower detection limit and limit of quantifications are 5.62×10 -10  M and 2.65×10 -8 respectively. The composite modified electrode showed good stability and reproducibility. The proposed method was successfully applied for the present investigation with a great assure as an economical and simple sensor with furthermore a shorter analysis time and further the sensor also used for heavy metal detection in real samples.