Polylactide (PLA)/cellulose nanocrystal (CNC) nanocomposites with 1, 3, and 5 wt% CNC contents were prepared through (a) solution casting and (b) dilution of solution-casted PLA/CNC masterbatch though melt mixing in a twin-screw extruder. The effect of preparation method on the CNC dispersion quality and hence the final properties of the nanocomposites were studied. A better CNC dispersion within PLA was obtained when using solution casting method, whereas the formation of CNC agglomerates was observed in the melt-processed nanocomposites. The rheological results confirmed that a solid network was formed at the CNC content of around 3 wt% in the solution-casted samples. The PLA crystallization could also be enhanced differently in the presence of CNC nanoparticles through various preparation routes. Moreover, the CNC incorporation noticeably enhanced the storage modulus of PLA beyond its glass transition temperature. The oxygen permeability of PLA was also remarkably reduced with CNC by employing both methods.