In the present article, we establish the numerical solution for the mixed Volterra- Fredholm integral equation (MV-FIE) in (1+1) dimensional in the Banach space L2[-1, 1] × C[0, T], T < 1. The Fredholm integral term is considered in the space L2[-1, 1] and it has a discontinuous kernel in position. While the Volterra integral term is considered in the class of time C[0, T], T < 1, and has a continuous kernel in time. The necessary conditions have been established to ensure that there is a single solution in the space L2[-1, 1] × C[0, T], T < 1. By utilizing the separation of variables technique, MV-FIE is transformed to Fredholm integral equation (FIE) of the second kind with variables coefficients in time. The separation technique of variables helps the authors choose the appropriate time function to establish the conditions of convergence in solving the problem and obtaining its solution. Then, using the Boubaker polynomials method, we end up with a linear algebraic system (LAS) abbreviated. The Banach fixed point (BFP) hypothesis has been presented to determine the existence and uniqueness of the solution of the LAS. The convergence of the solution and the stability of the error are discussed. The Maple 18 software is used to perform some numerical calculations once some numerical experiments have been taken into consideration.