Provided is a carboxylic acid-modified nitrile-based copolymer latex, and more particularly, provided are a carboxylic acid-modified nitrile-based copolymer latex which includes a carboxylic acid-modified nitrile-based copolymer including a monomer-derived repeating unit; and a repeating unit derived from a monomer represented by Chemical Formula 1 below, the monomer-derived repeating unit including a conjugated diene-based monomer-derived repeating unit, an ethylenically unsaturated nitrile-based monomer-derived repeating unit, and an ethylenically unsaturated acid monomer-derived repeating unit (see description of the present invention), a method for preparing a carboxylic acid-modified nitrile-based copolymer latex, a latex composition for dip-forming including the copolymer latex, and an article formed by the composition.