In this study, electromagnetic shielding effectiveness of some weft-knitted structures is investigated. For this purpose, weft-knitted structures are produced using copper wire/cotton incorporated yarns. Conductive yarns are produced by yarn-folding machine. Four knitted constructions (plain knitting, weft in-laid plain knitting, 1X1 rib, and weft in-laid 1X1 rib) are formed into knitted structures with conductive yarns by using 7G flat knitting machine. Electromagnetic shielding values of test samples are determined by a coaxial test fixture relating to ASTM D4935 test standards. Measurements are made in the frequency range of 27 MHz-3 GHz. The effect of conductive content, stitch density and fabric construction parameters are investigated considering the electromagnetic shielding performance of weft-knitted structures. Test results show that weft-knitted structures investigated in this study have 10-40 dB shielding effectiveness under the frequency of 500 MHz.