A theoretical expression for magnetic transition temperatures of binary rare‐earth alloys is proposed based on the similarity between the expressions of spin‐disorder resistivity and transition temperatures of pure rare‐earth metals. The proposed expression for the magnetic transition temperature for binary rare‐earth alloys iskTc (or Tp)=(−3&pgr;Z2)/EF&OHgr;2)&Sgr;Rn≠0&PHgr;(2KFR) × [x(1−x)Vab2 + xGa2(ga−1)2ja(ja+1)+(1−x)Gb2 (gb−1)2jb(jb+1)], where &PHgr;(2KFR)=(KFR×cosKFR‐ sinKFR)/(KFR)4and the other symbols have their usual meaning. The above expression is obtained from considering an equation for spin disorder resistivity given by Dekker. The experimental data of magnetic transition temperatures of Gd&sngbnd;Dy system have been used to test the validity of the proposed equation. The agreement between theory and experiment is reasonably good.