A numerical scheme is constructed for the problems in which the diffusion and convection parameters (1 and 2 , respectively) both are small, and the convection and source terms have a jump discontinuity in the domain of consideration. Depending on the magnitude of the ratios 1 ∕ 2 2 , and 2 2 ∕ 1 two different cases have been considered separately. Through rigorous analysis, the theoretical error bounds on the singular and regular components of the solution are obtained separately, which shows that in both cases the method is convergent uniformly irrespective of the size of the parameters 1 , 2. Two test problems are included to validate the theoretical results.