Multilevel image thresholding is effectually technique used to segment many types of images. It usually applied in image preprocessing phase. In this chapter, a review of gray level image segmentation using multilevel thresholding based on metaheuristic algorithms is introduced. Nine algorithms and their studies in multilevel thresholding segmentation are presented namely cuckoo search, bat algorithm, artificial bee colony, particle swarm optimization, firefly algorithm, social spider optimization algorithm, whale optimization algorithm, moth-flame optimization algorithm, and gray wolf optimization algorithm. The objective function, performance measures, and the number of images and thresholds that applied on the studies are mentioned. The review concludes that the multilevel thresholding segmentation is a challenge and many studies till now work to solve it.