In this paper, we use the asymptotical analysis to construct the asymptotic approximation of the solution with internal transition layer of the boundary value problem for a reaction-diffusion equation on the segment in case of discontinuous reactive and diffusive terms. The internal layer is located in the vicinity of a single point of discontinuity of the mentioned terms. We also investigate the existence and stability of such solution. For the last purpose, we use the asymptotical method of differential inequalities. KEYWORDS asymptotic approximation, discontinuous terms, lower and upper solutions, reaction-diffusion problem, small parameter Math Meth Appl Sci. 2018;41:9203-9217.wileyonlinelibrary.com/journal/mma