We consider a Canham − Helfrich − type variational problem defined over closed surfacesenclosing a fixed volume and having fixed surface area. The problem models the shape ofmultiphase biomembranes. It consists of minimizing the sum of the Canham − Helfrichenergy, in which the bending rigidities and spontaneous curvatures are nowphase-dependent, and a line tension penalization for the phase interfaces. By restrictingattention to axisymmetric surfaces and phase distributions, we extend our previous resultsfor a single phase [R. Choksi and M. Veneroni, Calc. Var. Partial Differ. Equ.(2012). DOI:10.1007/s00526-012-0553-9] and prove existence of a globalminimizer.