This chapter explores the impact of nanoparticle dispersion and type on the micromechanical properties and microstructure of geopolymer composites. Nano-SiO2 (NS) and nano-TiO2 (NT) were incorporated into fly ash-based geopolymers, with a focus on their dispersion effects and the resulting changes in the sodium aluminosilicate hydrate (N-A-S-H) gel phase. Proper dispersion of nanoparticles using sonication was crucial for optimizing the microstructure and micromechanical properties of geopolymers. Both NS and NT enhanced the early reaction rate and increased the proportion of N-A-S-H gel, but their effects on mechanical properties varied. Geo-NT exhibited higher micromechanical properties due to the high modulus of NT particles, while Geo-NS showed better macro-compressive strength due to better dispersion and bonding with the gel matrix. The study highlights the importance of nanoparticle dispersion and type in influencing the microstructure and performance of geopolymer composites.