Effects of Bi substitution upon magnetic and magnetodielectric properties of Y3Fe5O12 ceramics were investigated. It was found that the saturation magnetization decreases and the magnetic ordering temperature increases as the amount of Bi increases. The contribution of intrinsic and extrinsic effects to magnetodielectric effects decreases with increase of Bi, which results in the decrease of magnetodielectric coefficient of Y3−xBixFe5O12 ceramics.