A picosecond time‐resolved multiplex coherent anti‐Stokes Raman scattering (CARS) spectrometer based on a new principle has been constructed using a femtosecond laser, nanosecond lasers, and a streak camera. The second harmonic of the output from the femtosecond Ti:sapphire oscillator/regenerative‐amplifier system is used for the photoexcitation. The second harmonic of a nanosecond Nd:YLF laser is used as CARS probing &ohgr;1radiation, and the output of a nanosecond broadband dye laser is used as &ohgr;2radiation. CARS signals, which are generated from the sample during the nanosecond probing pulses, are analyzed in the frequency domain by a spectrograph and are resolved in the time domain by a streak camera. This enables us multiplex CARS measurements not only in the frequency domain but also in the time domain (termed two‐dimensional multiplex CARS). Consequently, CARS spectra at various delay times are obtainable with a single measurement. Owing to the short duration and high stability of the femtosecond pumping pulses, time resolution as high as 15 ps has been achieved. Picosecond time‐resolved CARS spectra of all‐trans retinal and &bgr;‐carotene are presented to demonstrate the high capability of the constructed system. The factors which determine the time resolution of this CARS spectrometer are discussed.