The high temperature approximation (HTA) for a polydisperse hard-sphere Yukawa chain fluid is proposed. A closed form analytical expression for Laplace transform of the reference system sitesite radial distribution function, which is used as an input in the theoretical scheme developed, is obtained from the solution of the averaged version of the multidensity Ornstein‐Zernike equation. It is demonstrated that in the frames of the HTA polydisperse hard-sphere Yukawa chain fluid model belongs to a class of “truncatable free energy models”, i.e. the models with thermodynamical properties (Helmholtz free energy, chemical potential and pressure) defined by a finite number of generalized moments. The accuracy of the theory is accessed by comparison of its liquid-gas phase diagram predictions obtained in the monodisperse limiting case, with the corresponding predictions of the statistical associating fluid theory for the potentials of variable range (SAFT‐ VR) and thermodynamic perturbation theory dimer (TPTD).