The present invention relates to a novel composition for improving the effectiveness of herbicides, to the use of this composition for improving the effectiveness of herbicides, to a herbicidal agent which comprises this composition and at least one herbicide, and to the use of this herbicidal agent for controlling undesired plant growth. The composition comprises: (a) at least one C1-C4-alkyl ester of at least one aliphatic C14-C22-carboxylic acid, where the at least one carboxylic acid consists to at least 70% by weight of aliphatic carboxylic acids having 18 carbon atoms； (b) at least one anionic surfactant which is selected from the esterification products of monohydroxy-functional alkyl polyethers with inorganic polyprotonic acids； (c) at least one aliphatic C14-C22-carboxylic acid； (d) optionally at least one antifoam； and (e) at least one aromatic solvent.
