Insulating SiAlON ceramics can be machined into complex shapes if the electrical conductivities can be increased with additives. Therefore, the microfluidization technique was used as an alternative to traditional sonication for exfoliation and homogenization of GNPs to investigate the effects of different exfoliation, size reduction and homogenization techniques on the microstructure, electrical conductivity and percolation threshold values of GNPs-SiAlON composites. 2.85, 5.70 and 11.40 vol. % sonicated and sonicated + microfluidized GNPs added into SiAlON matrix and were densified by using SPS technique. Due to their thinner and smaller platelet size, microfluidized GNPs dispersed more homogeneously compared to the sonicated GNPs in the SiAlON matrix. Electrical conductivities of the microfluidized GNPs-SiAlON composites were similar to 70-200% higher than sonicated GNPs-SiAlON in the both measured directions. Lower percolation thresholds were achieved when sonicated + microfluidized GNPs used in comparison to sonicated GNPs containing composites. Electrical conductivities in the in-plane direction were also higher than through-plane direction.