This paper presents a power efficient 60 GHz frequency doubler fabricated in a 130-nm SiGe-BiCMOS technology for conversion of an input signal at 30 GHz to an output signal at 60 GHz. In order to improve the conversion gain (CG) and bandwidth, the proposed frequency doubler is implemented by a Gilbert-cell topology utilizing a bootstrapping technique. To realize single-ended input and output, an active balun and a Marchand balun are designed at the input and output of the frequency doubler, respectively. This proposed design achieves up to 3.4 dBm output power at 59 GHz, with a maximum CG of 22.5 dB, and a 4.4% peak DC-to-RF efficiency. Moreover, measurement results show a 3-dB bandwidth of 15 GHz from 51 to 66 GHz and a maximum fundamental suppression of 45 dB. To the best knowledge of the authors, the proposed frequency doubler provides the highest CG at the operating frequencies.