The stress concentration and distribution around an inhomogeneity of threefold symmetry in a polycrystalline ceramic matrix is considered. The perturbation method in the theory of plane elasticity is used to solve the problem of a nearly circular inhomogeneity of threefold symmetry under remote loading in the first-order approximation. The solution was specified to the uniaxial tension of convex and concave rounded triangular inhomogeneities. The stress concentration on the interface as well as the stress distribution in both inhomogeneity and matrix along the inhomogeneity symmetry axes are studied and discussed in detail. The numerical results, obtained analytically with the first-order approximate solution, are compared with those of finite-element calculations.