In order to control the surface wettability of hyperbranched hydrophilic poly(amidoamine) (PAMAM)-grafted nano-sized silica, hydrophilic alkyl chain (CnH2n+1) with different chain lengths (n = 4, 8, 15) were postgrafted onto PAMAM-grafted silica by the reaction of terminal amino groups of PAMAM grafted on the silica surface with alkyl acid chlorides (CnH2n+1-COCl). The postgrafting of CnH2n+l-COCl increased with increasing PAMAM grafting and alkyl chain length Of CnH2n+1-COCl However, the terminal amino groups of PAMAM-grafted silica used for the postgrafting of CnH2n+1-COCl decreased with increasing chain length. This may be due to the steric hindrance between terminal amino groups of PAMAM-grafted silica and CnH2n+1-COCl: the steric hindrance is considered to increase with increasing chain length of CnH2n+1-COCl. The surface wettability was estimated by contact angle measurement for water and methanol wettability. As a result, it was found that contact angle and methanol wettability increased with increasing alkyl chain length of postgrafted CnH2n+1-COCl. The hyperbranched PAMAM-grafted silica readily dispersed in water and methanol because of the hydrophilic nature of grafted PAMAM, but it lost dispersibility in water and methanol due to postgrafting of hydrophobic chains.