A positive resist composition, which comprises: (A) a resin having a monocyclic or polycyclic alicyclic hydrocarbon structure, of which solubility in an alkali developer increases under an action of an acid; (B) a compound capable of generating an acid upon irradiation with actinic rays or radiation; (C) a resin having a repeating unit represented by formula (C) as defined in the specification; and (D) a solvent, wherein a content of the resin as the component (C) is from 0.1 to 20 mass % based on a solid content of the positive resist composition, and a pattern forming method using the same.