Photonics‐based microwave frequency mixing provides distinct features in terms of wide frequency coverage, broad instantaneous bandwidth, small frequency‐dependent loss, and immunity to electromagnetic interference as compared with its electronic counterpart, which can be a key technical enabler for future broadband and multifunctional RF systems. Herein, all‐optical and optoelectronic microwave frequency mixing techniques are reviewed, with an emphasis on the latest advances in photonics‐based microwave frequency mixers with improved performance in terms of conversion efficiency, dynamic range, mixing‐spur suppression, mixing functionality, and polarization independence. Innovative applications enabled by photonics‐based microwave frequency mixers, such as radio‐over‐fiber communication systems, radar systems, satellite payloads and electronic warfare systems, are also reviewed. In addition, efforts in implementing integrated photonics‐based microwave mixers that lead to a dramatic reduction in size, weight, and power consumption are also reviewed.