We describe the phase stability and suppressed → phase transformation in SiC/SiC fiber-reinforced composites prepared by spark plasma sintering (SPS), resulting in samples of >96% relative density and uniform -SiC microstructure. These samples are compared to ones produced by a hot pressing (HP) technique that results in samples with ~80% conversion to α-SiC hexagonal phases (4H and 6H). The phase transformation in the samples manufactured by SPS is shown to be significantly retarded due to the influence of lower sintering temperature, shorter processing time, and higher pressure. In addition, these samples exhibited hardness values in the range of 22 to 26 GPa, which were higher than those produced by HP, due to the higher density of the SPS samples, as well as relevant differences in phase composition. It was demonstrated that the → phase transformation is independent of fiber content in the composites. This study is of special interest for the production of SiC/SiC composite structures for electronic and structural applications.