In Helicobacter pylori, the major actor in post-transcriptional regulation is an RNA degradosome assembly composed of the essential ribonuclease RNase J and the DEAD-box RNA helicase RhpA. Here, we describe the oligomeric state and post-translational modifications of this protein complex. Our crystal structure of RNase J at 2.75 Å resolution reveals a homotetrameric quaternary state, and solution studies show that purified RNase J forms monomers and dimers, that RhpA is a monomer, and that the two proteins interact to form a stable complex with a 1:1 stoichiometry. Using mass spectrometry, we observed that RNase J is acetylated on multiple residues, one of which, K649, is important for RNase J oligomerization. Mutations targeting this residue and others affect the dimerization and in vitro activity of RNase J, suggesting that the dimer is the active form. In H. pylori, we observed that several of the identified acetylated residues impact on cell morphology, suggesting their importance for RNase J cellular function. Using H. pylori mutants, we found that several pathways contribute to RNase J acetylation. We propose acetylation as a regulatory level controlling RNase J properties and as a consequence the activity of the H. pylori RNA degradosome.