Disclosed is a room temperature curable silicon group-containing polymer composition containing a reactive silicon group-containing polymer (A) having a group represented by the formula (1) at an end of the main chain, which is obtained through a reaction between a polyoxypropylene polyol and a γ-isocyanate propyltrialkoxysilane, a curing catalyst (B), an amino-functional organosiloxane (C), and optionally an inorganic filler (D) which is surface-treated with glycol. Also disclosed is a room temperature curable silicon group-containing polymer composition which contains, as the reactive silicon group-containing polymer (A), a mixture of a polymer (A1) having a reactive silicon-containing group at two or more ends, which is obtained through a reaction between a polyoxypropylene polyol and a γ-isocyanate propyltrialkoxysilane, and another polymer (A2) having a reactive silicon containing-group only at one end, which is obtained through a reaction between a hydroxypolyoxypropylene having a hydroxyl group at one end and a γ-isocyanate propyltrialkoxysilane, a curing catalyst (B) and an amino group-substituted alkoxysilane (C1) or an amino-functional organosiloxane (C2).