In one aspect, the invention has an object of providing antifouling coating compositions which have high resistance to fouling, in particular, fouling by slime, can form coating films with excellent properties such as strength and rubber properties, exhibit appropriate viscosity (sprayability and coating film surface leveling properties during spray coating) and sagging resistance, and have high storage stability suppressing deteriorations of these properties. To achieve the object, the invention provides an antifouling coating composition including (A) a diorganopolysiloxane having at least two silanol groups in the molecule, (B) an organosilane and/or a partial hydrolyzate condensate thereof having at least two hydrolyzable groups in the molecule, and (C) a pyrithione metal salt. The antifouling coating composition can be prepared from a kit in the form of a multiple-component system including respective packages of a component including the component (A) and the component (C), and a component including the component (B). In the (kit for the preparation of the) antifouling coating composition, the pyrithione metal salt (C) functions as an effective ingredient for achieving excellent antifouling properties, in particular, anti-sliming properties, and also as an effective ingredient for improving storage stability.