Rheological behavior of reactively extruded starch-PCL nanocomposite blends was evaluated in an off-line capillary rheometer. Power law models for blends with different nanoclay volume fractions were developed using appropriate correction factors. Consistency coefficients K for blends containing starch were significantly higher than 100% PCL. Starch-PCL nanocomposite blends showed shear-thinning behavior with higher pseudoplasticity than did 100% PCL. Viscosities of nanocomposite blends were significantly lower than that of 100% PCL and nonreactive starch-PCL composites synthesized from simple extrusion mixing. Power law coefficients developed in this study will be used to evaluate rheology-dependent parameters during scaling up the reactive extrusion process from a batch micro-extruder to a high output continuous twin-screw extruder.