The chapter is concerned with generalization of different effective field methodsEffective field methods to account for imperfect contacts at phase interfaces when determining effective properties of micro-heterogeneous materials. The presence of imperfect contacts means a violation of continuity of some fields on the inner borders. Such contacts can appear due to the specificity of the process occurring on the meso-level, as well as due to the presence of microstructural features including defects of various natures. The problem can be related to various fields of mechanics. The presence of slip coating on particles of multi-component media leads to the necessity to account for imperfect contacts when determining effective viscosity. This, in particular, relates to problems of tribology. The presence of delaminations results in the necessity of consideration of imperfect contacts within a number of problems on the determination of effective properties, including effective conductivity, diffusivity, and elastic moduli. These, in turn, are related to thermodynamics and elasticity theory. The presence of segregation, which is the accumulation of impurities in defects, leads to the necessity to account for imperfect interfaces when determining effective diffusivity. This belongs to the problems of describing mass transport. The current research focuses on the problem of determining effective diffusivity, which can be expressed in terms of a second-order tensor.