Graphite/epoxy (Gr/E) composites have attractive properties—low density, high stiffness, and a low coefficient of thermal expansion (CTE)—that make them prime candidates for many spacecraft applications. The effects of a thermal cycling environment on the dimensional stability and microstructural integrity of Gr/E composites were evaluated. Severe microcracking was found in several high-modulus fiber (HMS)-reinforced 350°F-cure epoxy resin systems after exposure to 25 thermal cycles between the temperature of liquid nitrogen (−320°F) and that of boiling water (+212°F). A hybrid system combining Thornel-300 (T-300) fabric and HMS tape exhibited fewer microcracks, with the fabric acting as a crack stopper. Of the material systems investigated, a 250°F-cure system, HMS/CE 339, was found to be the most resistant to microcracking. The effects of thermal cycling on the microyield strength (MYS) and CTE of several near-zero expansion Gr/E composites were also studied.