The coefficients of thermal expansion (CTEs) of fiber reinforced composites play an important role in the design and analysis of composite structures. Since the thermal expansion coefficients of polymer matrix materials are typically much higher than those of fibers, and the fiber often exhibits anisotropic thermal and mechanical properties, the stress induced in the composite due to temperature change is very complex. Large discrepancies exist among the analytical models for the transverse CTE of unidirectional composites. Hence, it is problematic when choosing a suitable model. With the development of computer technologies, finite element analysis (FEA) proved its effectiveness in calculating the effective CTE of composites. In this study, the transverse CTEs of unidirectional carbon fiber composites were calculated by finite element analysis using a representative unit cell. The analytical micromechanical models from literature were compared against the FEA data. It shows that Hashin’s concentric cylinder model is the best. However, it is inconvenient for practical applications due to the amount of computation. In this study, based on the FEA data, an engineering model for predicting the transverse CTE of unidirectional composites was developed by regression analysis. This model was validated against the FEA and experimental data. It shows that the developed model provides a simple and accurate approach to calculate the transverse CTE of unidirectional composites.