An external additive for a toner includes: a particulate of a polymerization product of at least one silicon compound selected from a silane compound represented by Chemical Formula 1: Si(OR1)4 (wherein R1 is a C1 to C6 monovalent hydrocarbon group) and a hydrolysis-condensation product thereof. The particulate has the following properties: a number average particle diameter of about 50 nm to about 250 nm, a first specific surface area (α) measured by a gas adsorption method of about 13 m2/g to about 80 m2/g, and true density measured by a nominal volume expansion method of about 1.9 g/cm3 to about 2.1 g/cm3.