Two strains named ESC1T and ESC5 were isolated from nodules of Cytisus scoparius growing in a Spanish soil. Phylogenetic analysis of the 16S rRNA gene showed that these strains belong to the genus Ochrobactrum, their closest relatives being Ochrobactrum anthropi and Ochrobactrum lupini, with 100 and 99.9 % similarity to the respective type strains. Despite this high similarity, the results of DNA–DNA hybridization, phenotypic tests and fatty acid analyses showed that these strains represent a novel species of genus Ochrobactrum. The DNA–DNA hybridization values were respectively 70, 66 and 55 % with respect to O. lupini LUP21T, O. anthropi DSM 6882T and Ochrobactrum tritici DSM 13340T. The predominant fatty acids were C18 : 1 ω7c and C18 : 1 2-OH. Strains ESC1T and ESC5 were strictly aerobic and were able to reduce nitrate and to hydrolyse aesculin. They produced β-galactosidase and β-glucosidase and did not produce urease after 48 h incubation. The G+C content of strain ESC1T was 56.4 mol%. Both strains ESC1T and ESC5 contained nodD and nifH genes on megaplasmids that were related phylogenetically to those of rhizobial strains nodulating Phaseolus, Leucaena, Trifolium and Lupinus. From the results of this work, we propose that the strains isolated in this study be included in a novel species named Ochrobactrum cytisi sp. nov. The type strain is ESC1T (=LMG 22713T=CECT 7172T).