The roles of nano-silica particles in the morphology, rheological, crystallization, and melting properties of polyamide 6/acrylonitrile-butadiene-styrene (PA6/ABS) blends were investigated. With the addition of nano-silica particles possessing different surface characteristics (hydrophilic or hydrophobic), the blends showed a notable difference in the morphology of the dispersed ABS phase in the melt or solid state, which is mainly caused by different distribution states for the two kinds of nano-silica particles. Particularly, it was found that the hydrophilic nano-silica particles tended to distribute in PA6 matrix, whereas the hydrophobic nano-silica particles were almost located at the PA6/ABS interface. Besides, the shear thinning behavior of the composites was significantly changed with the incorporation of hydrophobic nano-silica particles and the contribution from the interface was regarded as the dominated one to influence the rheological properties. Finally, with different surface characteristics and their distribution states, it was found that nano-silica particles can play different roles in crystallization and melting properties.