This chapter focuses on synthesis and processing-microstructure relationships of multiwalled carbon nanotubes (CNTs) and SiC nanofibers with chemical vapor deposition (CVD). Various CNTs grown by CVD with anodic aluminum oxide (AAO) templates were examined with scanning and transmission electron microscope (SEM and TEM). It demonstrates that the experimental conditions, especially catalysts and plasma, have significant impact on CNT growth rates and microstructures. SiC diameters match well with the diameters of precursor CNTs, indicating SiC nanofiber size is controlled by the catalysts originated from CNTs. Generally, CNTs fabricated with CVD-template method have disordered graphitic structures and thus have lower tensile strength, but the disordered structures may help for the load transfer between graphitic layers. The chapter describes CVD-SiC nanofibers appear to be stiffer than multiwalled CNTs and may also serve as a good candidate for composite reinforcing materials.