An object of the present invention is to provide a treatment liquid for patterning a resist film and a pattern forming method, each of which can simultaneously suppress the occurrence of pattern collapse in a resist L/S pattern and the occurrence of omission failure in a resist C/H pattern.The treatment liquid of the present invention is a treatment liquid for patterning a resist film, which is used for subjecting a resist film obtained from an actinic ray-sensitive or radiation-sensitive resin composition to at least one of development or washing, and contains an organic solvent, in which the treatment liquid contains a first organic solvent having an SP value of 16.3 MPa1/2 or less and a second organic solvent having an SP value of 17.1 MPa1/2 or more.