Argonaute proteins are a family of highly conserved proteins existing in almost all known organisms. In higher eukaryotes, this family is comprised of two separate clades of proteins, the AGO proteins and the PIWI proteins. Canonically, AGO proteins act in the cytoplasm where they form the RNA induced silencing complex (RISC) along with an associated microRNA (miRNA) or short interfering RNA (siRNA) and act to regulate gene expression post-transcriptionally. Beyond their well described role in small-RNA mediated gene silencing in the cytoplasm, there is evidence that AGO proteins play a critical role in the male germline. Specifically, these proteins have been shown to localize to the the sex body, a specialized sub domain of the nucleus housing the sex chromosomes. Using a triple knockout mouse line (Ago413), we have shown that loss of Ago1, Ago3 and Ago4 leads to significantly decreased testis weights, sperm counts and litter sizes along with impaired motility and IVF fertilization rates as well several sperm head and tail defects. Most curiously however, mutant animals also show an increased variation in the sex ratios of individual litters. Analysis of motile sperm from Ago413 mutant males revealed a normal 1:1 ratio of X to Y bearing sperm, indicating that the bias observed in these crosses is not due to a disparity among the number of X and Y bearing sperm but instead might be due to differences in the functionality of the sperm or early developmental dysfunction in the embryo. In addition to this, we have also shown that Ago413 mutants display impaired silencing of the X and Y chromosomes in pachytene spermatocytes as evident by aberrant localization of markers such as γH2AX, ATR and TOPBP1 and an influx of RNA Pol II within the sex body. Gene set enrichment analysis of RNA-sequencing data confirmed this loss of silencing, revealing significant upregulation of genes found on the X and Y chromosomes of Ago413 mutant spermatocytes. Sequencing of small RNA populations from spermatocytes and spermatids of Ago413 mutant and wildtype males uncovered a previously characterized cluster of miRNAs residing on the X chromosome. This cluster, known as Fx-mir, is part of the Fragile X region and located within the Hstx2 locus. Taken together, these results clearly demonstrate a novel nuclear role for AGO3 and AGO4 during meiosis that is essential for proper silencing of sex chromosomes as well as downstream spermiogenesis.