Boule, a Drosophila orthologue of the vertebrate Dazl fertility factors, is a testis-specific regulator of meiotic entry and germline differentiation. Mutations inactivating either Boule, which is an RNA-binding protein, or Twine, which is a Cdc25-type phosphatase, block meiotic entry in males. Here we show that twins and boule interact genetically. We also find that protein expression from twine messenger RNA correlates with cytoplasmic accumulation of Boule and is markedly reduced by boule mutations. Remarkably, heterologous expression of Twine rescues the boule meiotic-entry defect, indicating that the essential function of Boule at the transition from G2 to M phase during meiosis is in the control of Twine translation.