Spermatogenesis is a cell differentiation programme that allows a normally dividing diploid cell to become haploid and to acquire the morphological characteristics required to reach and to fertilize the female gamete. Many of the steps involved in this differentiation programme necessitate profound modifications of the genome, rendering it unable to play its template role for the synthesis of mRNAs. Therefore, de novo transcription is not a continuous process during germ cell differentiation and many mRNAs need to be synthesized and stored at specific times to be available during the transcriptionally inactive stages of spermatogenesis. Germ cells express high levels of RNA-binding proteins that assist these post-transcriptional events. The generation of mouse knockout models has highlighted the essential role played by many of these RNA-binding proteins for the correct progress of spermatogenesis and for the formation of a fertile male gamete. Herein, we review the major findings on the role of RNA-binding proteins in mammalian spermatogenesis.