Small resonator antennas, such as metaresonator antennas, have narrow bandwidths, which limits their effective range of frequencies. When they are used as embedded antennas in building materials, their performance is affected more than other types of antennas, as typical building materials have a shielding effectiveness (SE) of 80 dB to 100 dB. Adding magnetic and/or metallic particles to cement mixes changes the properties of the concrete, which can improve the performance of antennas. Specifically, enhancing a cement paste with iron-based magnetic particles improves the bandwidth and S11 of embedded antennas. This report investigates the impact of two different iron-based magnetic particle sizes (micro- and nanosized particles) to determine the effects that they have on the S11 and S21 characteristics of the metaresonator antenna array embedded in enhanced cement pastes. Results show that compared to cement paste only sample, cement paste with micro-sized iron-based magnetic particles had the greatest improvement of performance of a metaresonator antenna array in terms of a small shift in the resonance frequency and an increase of bandwidth. Particularly for a cement paste enhanced with micro-sized iron (III) oxide particles, the S21 curve was improved over the cement paste only sample by as much as 10 dB.