The quality of nanocrystalline cellulose (CNC) dispersion in polymer nanocomposites depends on the following factors: (i) the morphology of CNC agglomerates used in the preparation of the nanocomposite; (ii) the strength of the agglomerates relative to the stresses that are available in melt processing equipment, such as extruders and mixers; and (iii) the surface energies of the matrix and the CNC and their surface energy interactions, at both application and processing temperatures. A dispersion factor was proposed to indicate the dispersibility potential of nanoparticles in various matrices. We have shown that currently available CNC agglomerates, normally produced by spray drying (CNCSD) or freeze drying (CNCFD) of CNC dispersions, tend to have a smooth, hard skin, low porosity, and strong resistance to breakdown in melt processing equipment. On the other hand, we found that if the agglomerates were produced by spray freeze drying, then more open and porous agglomerate morphologies were obtained. Such structures permit more ready penetration and wetting by the polymer melt during melt processing. Moreover, the morphology and structure of the spray freeze dried CNC (CNCSFD) agglomerates depend on the CNC concentration in the initial CNC/water dispersion. Low concentrations produce two-dimensional networks of CNC nanofibers, while higher concentrations yield three-dimensional porous spherical or ellipsoidal agglomerates. We were able to use such agglomerates to produce nanocomposites by melt processing of CNCSFD with polypropylene (PP) and poly(lactic acid) (PLA). The quality of dispersions in nanocomposites obtained using CNCSFD was substantially better than that generated with either CNCSD or CNCFD. Experimental evidence was obtained using electron microscopy, rheology, mechanical Properties, and crystallization behavior of nanocomposites, in conjunction with both PP and PLA as matrices. Keywords: Cellulose Nanocrystals; Nanocomposites; Dispersion.