A compact dual-band square slot loop rectenna fed by a microstrip line (MSL) for 2.4- and 5.8-GHz bands is presented. Instead of exploiting resonances of integer multiples of full wavelength in conventional dual- or multi-band slot loop antenna design, it is for the first time that the half-wavelength and one-wavelength resonant modes of MSL-fed slot loop antennas are exploited in the design of dual-band rectenna. Due to the distinct impedance behaviors at the two resonances, a matching circuit is inserted in between the rectifier circuit and slot loop radiator for simultaneous conjugate match at the two resonances. For verification, a prototype of the proposed compact slot loop rectenna for operation at 2.4- and 5.8-GHz bands is fabricated and tested. The conversion efficiencies of 49% and 66% are achieved, respectively. The prototype rectenna measures only 13 mm × 24 mm or 0.106λ 0 × 0.196λ 0 at 2.45 GHz.