Microelectromechanical systems (MEMS) energy harvesting devices have had limited commercial success partly due to the frequency mismatch between the device and the vibration source. Tuning the cantilever device is one possible solution but developing a tunable MEMS device is difficult. This paper demonstrates a novel method of tuning a MEMS cantilever device post-fabrication by using light-responsive azobenzene liquid crystal polymers (LCP). Light exposure causes the photoresponsive polymers to change their elastic modulus, thus affecting the resonant frequency of the device. The photoresponsive polymer was integrated with three different MEMS cantilever substrates including LCP, parylene, and silicon. The three cantilever beams all demonstrated changes in resonant frequency when exposed to UV light of 10.4%, 8.13%, and 4.86%, respectively. The change in resonant frequency is dependent on the stiffness of the substrate, the thickness of the azo-LCP, the intensity and duration of the light exposure, and the wavelength of the light. The results in this paper validate that light responsive polymers can be used to reduce the frequency of MEMS cantilevers post-fabrication, which could lead to developing devices that can be precisely tuned for specific applications.