Addition of lipophilic polyoxyethylene dodecyl ether (C₁₂EO_n) to the dilute micellar solution of polyoxyethylene phytosterol (PhyEO_m m = 10 and 20) results in the increase in viscosity. The increase in viscosity is attributed to the C₁₂EO_n induced one-dimensional micellar growth leading to the formation of worm-like micelles. Steady and oscillatory shear rheological measurement in PhyEO_m + C₁₂EO_n (n = 2-5) shows that on decreasing the EO chain length of C₁₂EO_n, in general, the one-dimensional micellar growth becomes increasingly favorable. However, with very short EO-chain, for example, C₁₂EO₂, phase separation occurs at a lower concentration before significant micellar growth can be induced. In the systems of C₁₂EO₃ and C₁₂EO₄, the wormlike micelles entangle to form a viscoelastic transient network having a dynamic rheology that can be described by Maxwellian model in wide range of shear frequency. It was found that increasing the concentration or decreasing the EO-chain length of PhyEO_m in the mixed system favors one-dimensional micellar growth. Comparison of the rheological behavior of PhyEO_m + C₁₂EO_n systems with that of polyoxyethylene cholesterol (ChEO_m) + C₁₂EO_n systems at similar conditions shows that in the former system C₁₂EO_n can induce micellar growth more effectively, which is attributed to the additional branching of the alkyl chain in the lipophilic moiety of the amphiphile.