We extended the scaled particle theory of Cotter and Wacker for multicomponent systems of straight hard spherocylinders to multicomponent solutions of wormlike hard spherocylinders and calculated phase diagrams of ternary systems consisting of two homologous semiflexible polymer components with different lengths and a low molar mass good solvent. The basic parameters in this theory are the chain contour lengths (L(1), L(2)), the hard core diameter (d), and the persistence length (q) of the polymer components. The theoretical ternary phase diagrams calculated by this scaled particle theory for wormlike hard spherocylinders were compared with experimental ternary phase diagrams obtained previously for systems of schizophyllan + water and poly(n-hexyl isocyanate) + toluene. When the hard core diameter d was chosen to have a value close to that estimated from the osmotic pressure or solvent chemical potential data for the corresponding binary solutions, good agreements between experimental and theoretical ternary phase diagrams were obtained for the isotropic-anisotropic binodal curves and the tie lines of all the systems compared. On the other hand, the present theory failed to predict anisotropic-anisotropic-isotropic three-phase coexistence as well as anisotropic-anisotropic two-phase coexistence in ternary solutions containing two samples with the Kuhn segment numbers N-1 (drop L(1)/2q) = 0.930 and N-2 (drop L(2)/2q) = 0.0765, whereas these multiphase separations were found for aqueous solutions of schizophyllan with the same N-i’s. When N-2 was decreased to smaller than 0.07 with N-1 kept at 0.93, these phase-coexisting regions appeared in the theoretical phase diagram.