Heterogeneous composites such as functionally graded materials are often characterized by their macro-level spatially dependent material properties. These features garner the ability to create structures with enhanced or desirable system response by coupling desirable attributes of each phase (e.g., thermal, mechanical, electrical, etc.) to create materials with overall improved efficiency through microstructural tailoring. For example, this unique class of material finds useful application in aerospace industries as multifunctional thermal barrier coatings (TBCs) and thermal protection systems (TPS). While the effective properties and thermostructural response of this class of materials has been receiving a great deal of attention, little effort has been given to the estimation of graded materials with manufacturing defects such as voids and porosity. Thus, this work explores the effects of porosity on the estimation of the effective properties and the effective thermal and thermomechanical response of spatially tailored metal-ceramic composites. Effective properties are evaluated using a detailed finite element model of three-phase graded materials which incorporates the effects of grading and the influence of particle interactions on the overall material response. The proposed three-phase porous model is found to be in good agreement with experimental data found in literature. The effects of quantity and distribution of porosity are studied by modeling and evaluating the response of graded Ti/Zr composed of varying magnitudes and dispersions of void content. The effective properties are found to be a function of the void content and the spatial distribution of the porosity phase. Effective elastic properties degrade, while thermal properties show improvement and thermoelastic properties exhibit little to no change. The effect of porosity on the overall thermostructural response is investigated by comparing the transient thermal response and thermomechanical behavior of porous Ti/Zr graded materials to that of a traditional Ti/TPS configuration. Here it is found that incorporating spatial variation can reduce through-thickness temperature gradients and stress concentrations found in conventional TPS. Furthermore, increased levels of porosity are found to reduce the benefits of grading with increases in temperature and stress gradients.