Abstract: To address the critical trade-off and urgent demand for balancing mechanical and electromagnetic properties in the integrated design of lightweight, radar-absorbing, and load-bearing aerospace composite structures, this paper proposes an absorbing-foam-filled hybrid carbon/glass fiber circular honeycomb sandwich structure (FFCH). Utilizing a straightforward layup design, the FFCH exploits the highly anisotropic mechanical and electrical properties of unidirectional carbon fiber tapes (UD-CF) in the transverse and longitudinal directions. Specifically, the hybrid carbon/glass fiber circular honeycomb walls are constructed by combining out-of-plane UD-CF with glass fiber fabric (GFF). Additionally, polymethacrylimide (PMI) radar-absorbing foam is filled into the honeycomb cells. By leveraging the mechanical and electromagnetic coupling effects among the core constituents, a collaborative design that synergistically optimizes both microwave-absorbing and load-bearing performance is successfully achieved. Electromagnetic (EM) simulations and experimental characterizations demonstrate that the carbon fibers aligned along the out-of-plane direction effectively mitigate the skin effect of EM waves and expand the regions of intense electric fields. Consequently, compared to the FFCH without carbon fibers, the average reflection loss of the proposed FFCH is further reduced from −10.2 dB to −12.1 dB in the low-frequency band of 2–6 GHz, and from −14.7 dB to −15.5 dB across the broader 2–18 GHz range. Furthermore, it is verified that the FFCH successfully achieves broadband (2-18 GHz), wide-angle (spanning 0°-60°), and high-intensity (with an average reflection loss to −15.5 dB) EM wave absorption capabilities. Out-of-plane compression test results indicate that, compared to the hybrid carbon/glass fiber circular honeycomb sandwich structure without foam infill (CH), the specific compressive strength and specific energy absorption of the FFCH are significantly improved by 65.40% and 60.87%, respectively. Finite element (FE) simulations further reveal the enhancement mechanism underlying its load-bearing capacity: the lateral support provided by the absorbing foam effectively suppresses the wrinkling buckling of the circular honeycomb walls. This shifts the failure mode of the structure from global buckling in the CH to local crushing in the FFCH, thereby substantially elevating the peak load-bearing capacity. The Ashby charts demonstrate that, compared to conventional foams, honeycombs, and various newly developed lightweight, high-strength sandwich topologies widely utilized in engineering, the FFCH exhibits a superior specific compressive strength. This highlights its more pronounced lightweight load-bearing advantages. By utilizing carbon fibers simultaneously as electromagnetic loss elements and primary load-bearing components, the FFCH achieves an integrated design of both mechanical and microwave-absorbing properties. This offers a highly promising design paradigm for lightweight, radar-absorbing, and load-bearing multifunctional composite sandwich structures.