The complete genome sequence of Sphingomonas sp. strain 7/4-4, which was isolated from the root nodule of the circumpolar legume Astragalus tugarinovii Basil, is reported. The assembly contains 4,423,370 bp in 1 circular chromosome, with a GC content of 65.94%. The genome sequence of strain 7/4-4 could provide insights into the metabolic potential of Arctic rhizobacteria.