RNA decay and RNA maturation are important steps in the regulation of bacterial gene expression. RNase J, which is present in about half of bacterial species, has been shown to possess both endo- and 5' to 3' exo-ribonuclease activities. The exonucleolytic activity is clearly involved in the degradation of mRNA and in the maturation of at least the 5'end of 16S rRNA in the two Firmicutes Staphylococcus aureus and Bacillus subtilis. The endoribonuclease activity of RNase J from a number of species has been shown to be weak in vitro and 3-D structural data of different RNase J orthologs has not provided a clear explanation for the molecular basis of this activity. Here, we show that S. aureus RNase J1 is a manganese dependent homodimeric enzyme with strong 5' to 3' exo-ribonuclease as well as endo-ribonuclease activity. In addition, we demonstrated that SauJ1 can degrade efficiently 5'triphosphorylated RNA. Our results highlight RNase J1 as an important player in RNA turnover in S. aureus.