The crystals of layered compounds are normally in the shape of disks or plates. Systematic experiments revealed that regular-shaped α-zirconium phosphate crystalline disks with a size-to-thickness ratio from 1 to 50 and size polydispersity as low as 0.2 can be obtained through hydrothermal treatment in 3 M to 15 M phosphoric acid solutions. Transmission and scanning electron micrographs revealed that the growth of the disks is mediated by oriented attachment, which happened continuously throughout the hydrothermal treatment between various sized disks. Ostwald ripening is effective in improving the regularity of the shape of the disks, especially under prolonged hydrothermal treatment. Preferred attachment among the flat surfaces of the disks leads to the diverse developments of their size and thickness polydispersities.