Silicon carbide (SiC) fibers can act not only as a load-bearing component, but also as a piezoresistive and microwave lossy material when embedded in fiber-reinforced polymer composites. By leveraging these multifunctional characteristics, we propose simultaneous self-sensing and microwave-absorbing composite structures based on embedded SiC fiber networks. A SiC fiber network consists of SiC fiber yarns embedded in each interlaminar of the host composite at regular intervals. The SiC fiber yarns, which do not come into contact with other SiC fiber yarns, act as independent sensing elements using their piezoresistivity. By positioning the SiC fiber yarns at regular intervals within the wavelength of the targeted microwave-absorption bandwidth, the SiC fiber network functions as a microwave lossy material. In this study, specific focus has been placed on designing a multi-functional composite that senses external impacts and also absorbs microwaves in the X-band (8.2–12.4 GHz). The simultaneous self-sensing and microwave-absorbing performance of the fabricated SiC-embedded composite was experimentally verified through microwave return loss measurements and dynamic signal acquisition tests. The proposed SiC fiber network-embedded composite structure has great potential for use in future aerospace structures.