ErAl 3 (BO 3 ) 4 crystals were successfully grown by the slow-cooling method in a K 2 Mo 3 O 10 flux. The formation of ErAl 3 (BO 3 ) 4 crystals was greatly dependent on the solute concentration of starting mixtures, and mixtures containing a solute of 32-41 mol % produced ErAl 3 (BO 3 ) 4 crystals. The obtained ErAl 3 (BO 3 ) 4 crystals had sizes up to 2.4 × 1.4 × 1.2 mm and a transparent pearl pink color. Their form was a hexagonal {112 h0} prism with pyramidal {101 h1} end faces.