Background and aims In Morocco’s semi-arid and sub-humid climates, the fodder legume Lupinus luteus is cultivated for its high economic and ecological value. In this work, we characterized some microsymbionts of L. luteus isolated by trapping from plants grown in soils of the agricultural area of Zaer, Morocco. Methods The phenotypic and genotypic diversity, the plant growth-promoting abilities, and the symbiotic efficiency of rhizobia isolated from root nodules of L. luteus were analyzed. Results Based on their REP-PCR fingerprinting results, eighteen strains were selected for Multilocus sequence analysis (MLSA) using rrs, glnII, gyrB, recA, and rpoB housekeeping genes, which revealed that all the strains belong to the genus Bradyrhizobium. Some strains were close to B. lupini and B. canariense. However, the remaining strains grouped apart from all described Bradyrhizobium species. Phylogenetic analysis of the nodA and nodC symbiotic genes showed that all the strains are members of the symbiovar genistearum. Quantitative evaluation of selected plant growth-promoting activities showed that the strains solubilize phosphate, and produce auxins and siderophores. All the strains used as inoculum in greenhouse experiments significantly improved the growth of L. luteus under nitrogen-free conditions. Conclusions Bradyrhizobium lupini and B. canariense are the main rhizobia nodulating L. luteus in the Zaer region. In addition to their high nitrogen fixation efficiency, these isolates also exhibit plant growthpromoting activities. These results highlighted one of the major reasons for the success of yellow lupine in this area without nitrogen fertilizers and pointed to the possibility of formulating these rhizobia into an effective inoculum for L. luteus