A resin composition includes: a polyol (A) having at least two OH groups; a polyfunctional isocyanate compound (B); a catalyst (C); and a compound (D) that undergoes keto-enol tautomerization, in which: a content ratio of the polyfunctional isocyanate compound (B) with respect to 100 parts by weight of the polyol (A) is 1 part by weight to 100 parts by weight; and the catalyst (C) includes an iron-based compound containing iron as an active center thereof. The resin composition can serve as a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer containing a polyurethane-based resin. Also provided are a pressure-sensitive adhesive sheet and a surface protective film each including such pressure-sensitive adhesive layer.