In many species, genes required for early embryogenesis are maternally expressed, but their translation is repressed in the oocyte, and this repression is essential for proper oocyte maturation. Although a number of RNA-binding proteins involved in maternal translational repression have been identified, the underlying mechanisms remain incompletely understood. Now, using zebrafish, Yonghua Sun and colleagues identify Nanog, best known as a pluripotency factor in embryonic stem cells, as a key mediator of translational repression in the oocyte. They show that maternal nanog mutants display derepression of translation, and this is associated with elevated endoplasmic reticulum stress, impaired oocyte maturation and defects in early embryogenesis. Through transcriptomic analysis, the authors find that the translation elongation factor eef1a1l2 is upregulated in nanog mutants, and show that maternal depletion of eef1a1l2 can significantly rescue the nanog mutant phenotype. Nanog binds directly to the eef1a1l2 promoter and appears to act as a transcriptional repressor to silence this translation factor in the oocyte. This study reveals an early role for Nanog - prior to its better-known function as a transcriptional activator in the early embryo - and helps to elucidate the mechanisms by which maternal mRNAs are silenced during oocyte maturation.