We propose a technique to simultaneously stabilize relative wavelengths among multiple diode lasers by using multiplexed photorefractive gratings. Each grating is designed to be Bragg matched for the counter-propagating reflection at a specific diode laser wavelength. Experimental results from stabilization of two diode laser wavelengths by using two photorefractive gratings exhibit excellent short-and long-term wavelength stability. We show that this technique can be extended to stabilize relative wavelengths of many diode lasers. The thermal stability of the photorefractive gratings and the signal-to-noise ratio (or the bit-error rate) are discussed.