This study involves measurement and evaluation of the electromagnetic shielding effectiveness (EMSE) in the X-band frequency range of rib-knitted fabrics formed from hybrid conductors. Hybrid conductive fabrics were made by knitting copper, silver, and stainless steel conductors together with cotton yarn. The basic theory of EMSE is introduced, and the waveguide measurement setup described. The through-reflect-line calibration setup was used to obtain accurate results. After calibration of the established waveguide measurement setup, hybrid conductive fabrics were tested. The measurements were analyzed and the fabrics compared. The aim is to produce a hybrid fabric that is suitable for general use, has a good EMSE, is easy to produce, and offers low-cost high-frequency solutions. An easy-to-produce and low-cost EMSE material is required, especially in new-generation wearable flexible electronic devices and military applications.