We studied the prevalence of ovotestis in western Altantic lionfish in order to advance our understanding of their reproductive biology. In addition, this work serves as one of the first characterisations of ovotestis in a reef species. We found that 15% of lionfish from North Carolina and the Bahamas displayed ovotestis. We also found that 3 of 884 individuals displayed fully mature oocytes, a rarely described occurence. The gonads of these individuals were also morphologically similar to ovaries, however the primary tissue composing the gonad was clearly spermatogenic. Figure Legend: I)late primary growth oocyte. II) Cortical alveoli oocyte. III) Vitellogenic oocyte. IV) Maturation oocyte. All scale bars are 100 μm.