Single crystals of Mn-Zn Ferrite were grown by slow cooling method using Na2B4O7 as flux agent. The effects of flux content and cooling rate on the types of crystals, and the relation between supersaturation and growth mechanism were studied. As a result, the types of grown crystals occurred as plate, hopper and octahedral crystals. The occurrence of these crystal types was dependent on flux content. The habit was found to correlate with the growth rate and supersaturation. The lateral growth of a dendritic crystal is related to the twin layer. The growth of crystals from borax melts mainly occurred by the layer-spreading growth following corner and edge nucleation caused by high supersaturation in the melt. Especially, the plate crystals were produced on top of the melts. The hopper and octahedral crystals occurred at lower supersaturation than the plate crystals.