An analytical model is developed for the sintering kinetics of ceramic dual-phase composites of the cathodes in solid oxide fuel cells (SOCFs). The model simulates the isothermal and pressureless sintering processes and formulates volumetric three-phase boundary (TPB) length and porosity as a function of sintering time, surface/interface energies, grain-boundary diffusivities, particle sizes, and dual-phase composition. Lanthanum strontium manganite (LSM)-yttria-stabilized zirconia (YSZ) composite is used as an example to develop and validate the model. LSM-YSZ composites are sintered at 1100 degrees C for various sintering time, and the TPB length and porosity are estimated from SEM images by using stereological analysis to validate the model. Parametric studies are performed at various conditions, illustrating novel insights into the sintering kinetics. This analytical model is generic and applicable to the sintering kinetics of ceramic dual-phase composites for use in solid-state electrochemical devices, such as SOCFs, electrolyzers, and gas separation membranes. This analytical model can also be easily extended to the sintering processes of other ceramic dual-phase and triple-phase composites.