Friction Stir Welding is a solid-state joining technology increasingly being applied to aluminum and other alloys in the automotive and aerospace industry due to its advantages in microstructure and mechanical properties over conventional welding techniques. To further enhance the mechanical properties of the weld, post-weld solution heat treatment (PWSHT) is one option. Previous research has shown that Abnormal Grain Growth (AGG) usually occurs in the weld nugget during PWSHT due to nugget instability at elevated temperatures. The current investigation is conducted to understand AGG in AA2195 FSW nugget during PWSHT and to determine the effect of several factors like the effects of initial temper of the welded plate and the weld process parameters, the effect of annealing and plastic deformation (work hardening), temperature at which the weld is deformed (cold and hot processing) and also the PWSHT time. It was found that the initial temper does not significantly affect the as welded nugget microstructure. Results indicate AGG to be dominant in the nugget regions, which have smaller as-welded grain size and with residual strain. Sufficient work hardening (deformation at room temperature) was found to suppress AGG during subsequent SHT. Whereas, AGG prevails when deformed at high temperatures.