The excellent physical properties of Polyamide 6,6, (PA66) result from the cooperative interactions within the semi-crystalline microstructure of the polymer. Several factors drive the development of the microstructure on cooling, including melting temperature and the amount of shear to which the melt is subject prior to solidification. These two factors contribute to the amount of specific work (MPa) introduced to the melt. In this study, samples were prepared using rotational rheometry to introduce a known amount of specific work to each sample. The range of specific work studied spanned from 6.25 MPa to 200 MPa. After shearing, the polymer was allowed to solidify and was then sectioned for subsequent thermal analysis. Crystallization studies using fast scanning calorimetry (FSC) were designed to isolate the peak time of crystallization for several previously-sheared samples of PA66 in five-degree increments across the temperature range of 85°C – 220°C. In the high-temperature range, peak time of crystallization decreased with increasing specific work, indicating flow-induced effects on the nucleation process for PA66. To a lesser extent, accelerated crystallization was also observed for the low-temperature crystallization processes. Interestingly, the temperature at which PA66 transitions from the high-temperature to low-temperature crystallization mechanism shifted to lower temperatures with increasing specific work. ESEM imaging of PA66 subject to strategic isothermal/specific work combinations reveals a shift in microstructure as a function of specific work and isothermal crystallization temperature.