Results from microcompression testing of micron-sized saltwater individual kaolinite flocs with different ageing times of up to 152 days show that the rearrangement of flaws or weak links towards a more uniform distribution contributes to the thixotropic increase in floc mechanical properties. Evidence of this newly identified thixotropism of clay flocs is provided by the Weibull moduli of floc stiffness and yield shear strength, which are well fitted using the stretched exponential thixotropy model. The Weibull modulus is a good quantitative descriptor of the thixotropic evolution of clay floc microstructure.