Detailed studies of growth of yttrium iron garnet (YIG) in the flux system Na₂O-B₂O₃ were made to delineate the phase stability regions of YIG and the neighbouring crystalline phases, and a tentative working diagram of Na₂O-B₂O₃-YIG in air was drawn from the results of small batch crystal growth runs and solubility studies. The occurrence of a rather narrow field of YIG crystallization in this system was explained on the basis of relative solubilities of different oxides constituting YIG. Several long-time growth runs with some typical compositions were carried out in this system to evaluate its suitability for bulk growth of YIG crystals. The system, although possessing some inherent advantages, was found to suffer from limitations because of which the maximum size of the self-nucleated crystals grown hardly exceeded 2.00 mm.