Improved dimensional stability of composites is desired in applications where they are exposed to varying temperature conditions. Polymers inherently have a high coefficient of thermal expansion (CTE), which complicates their inclusion in structural designs exposed to temperature extremes. However, through low-CTE reinforcements dispersed in a polymeric matrix, the CTE of the composite can be lowered to a degree suitable for use in service. This chapter aims at summarizing the studies that analyze the effect of vapor-grown carbon nanofibers (CNFs) on the thermal expansion behavior of polymer matrix composites. CNFs typically have a significantly lower CTE than epoxy resins and other widely used polymer matrices, which result in composites with increased dimensional stability as the dispersed CNF content is increased. The use of nanofibers has resulted in the ability to tailor the thermal expansion of the composite over a wide range. Schapery’s model is used to estimate the upper and lower bounds on the CTE of CNF/epoxy nanocomposites. The experimental results are found to be within the bounds.