Millimeter mixers have been fabricated from epitaxial films of Tl2CaBa2Cu2O8, using a bowtie antenna structure integrated with grain‐boundary weak links that were deliberately formed during film growth. The bowtie antenna was utilized for broadband millimeter wave coupling of the radiation into the weak links. Heterodyne mixing of signals at bothVband (55 GHz) andWband (94 GHz) frequencies, and subharmonic mixing atVhas been observed at liquid nitrogen temperature for zero and finite bias voltage conditions. The dependence of the IF output on temperature, bias voltage, and millimeter wave signal power has been studied. Efficient mixing with bias voltage exhibited strong signals right up toTc(101 K).