The effects of an inhomogeneous interphase on thermal response of fiber-reinforced composites are investigated in this paper. The work is based on a linear variation of Young's modulus and thermal expansion coefficient of the interphase and the assumption of generalized plane strain. An accurate analytical approach is presented to determine thermal stresses in composites reinforced with isotropic fibers containing an inhomogeneous interphase. How the inhomogeneous interphase, and Young's modulus and thermal expansion coefficient of the matrix affect thermal response of the composites is examined. It is found that the inhomogeneous interphase causes different stress distribution from that of the homogeneous interphase. Raising Young's modulus and thermal expansion coefficient of the matrix obviously increases the maximum radial, circumferential and axial stresses in all the constituents of the composites.