Clavibacter michiganensis subsp. sepedonicusis is a Gram-positive actinomycete that is the causative agent of the potato disease ring rot. Here, we announce the complete genome sequence of the Clavibacter michiganensis subsp. sepedonicusis siphophage CN1A. CN1A is only the second fully sequenced Clavibacter michiganensis subsp. sepedonicusis phage reported to date. Core and unique features of its genome are described.