Optical green emitting microresonators with high values of nonlinearity are desired for high optical up-conversion energy storage and lasing applications. Here we report on the synthesis of benzylammonium lead iodide (BALI) perovskite microcrystals made via antisolvent diffusion method. The use of polystyrene (PS) matrix helps the growth of environmentally stable BALI nanocrystals as a result of polymer capping. Optimization of the ratio of BALI-PS during the self-assembly process leads to the formation of defect-free composite microspheres. Further, these BALI crystals act as an active material within the microsphere resonators that display whispering gallery modes (WGM). These WGMs are responsible for high optical storage energy of resonators evidenced by their Q-factor as high as ∼1180. Two-dimensional finite difference time-domain calculation shows the concentration of the electric field near the microspheres boundary within a small mode volume of 1.83 μm3. Remarkably, BALI-PS composite microresonators and their neat crystals exhibit brilliant two-photon luminescence upon excitation by the infrared fundamental radiation. This simplistic microresonators fabrication technique provides a route toward low-cost nonlinear optical microlasers and other optical energy devices useful for various applications. © 2018 American Chemical Society.