The micromechanical approach of Simplified Unit Cell Method (SUCM) in closed-form three dimensional solutions is used for predicting creep response of unidirectional fiber reinforced composites. The composite consist of elastic fibers reinforcing nonlinear viscoelastic resin. The nonlinear viscoelastic matrix behavior is modeled by using Schapery single integral viscoelastic constitutive equation. Off-axis specimens of graphite/epoxy with 45 and 90 fiber orientations were subjected to 480 minutes creep tests and the results is compared with experimental data and MOC results available in the literature. There is good agreement with experimental results due to using SUCM.