<p>Salinity stress, through restricting water availability and inducing ion toxicity, represents one of the major threats to global agricultural productivity. Although plant growth-promoting bacteria (PGPB) have been widely studied for their ability to alleviate abiotic stresses, the co-inoculation of <i>Stenotrophomonas maltophilia</i> (MN099392) and <i>Rhizobium leguminosarum</i> bv. <i>phaseoli</i> (PP125713) to enhance salt stress tolerance in common bean (<i>Phaseolus vulgaris</i> L.) cultivars has received limited attention. This study aimed to evaluate the effects of co-inoculation with <i>S. maltophilia</i> and <i>R. leguminosarum</i> bv. <i>phaseoli</i> on physiological traits and yield performance of two common bean cultivars (Almas and Pak) under salinity stress. A factorial experiment was conducted based on a completely randomized design with three replications in the research greenhouse of the Faculty of Agriculture, Shiraz University. Treatments included six bacterial inoculations (non-inoculated control, <i>S. maltophilia</i> (P1), <i>Enterobacter hormaechei</i> (P2), <i>R. leguminosarum</i> bv. <i>phaseoli</i> strain Rb-114 (RB), and dual combinations P1 + RB and P2 + RB) and four salinity levels (0.5, 4, 6, and 8 dS m^− 1). Increasing salinity reduced chlorophyll and carotenoid contents, protein accumulation, and grain yield, while electrolyte leakage, proline concentration, antioxidant enzyme (APX and POD) activities, and ABA content increased. Co-inoculation with P1 + RB effectively mitigated the adverse effects of salinity by enhancing chlorophyll, carotenoids, soluble sugars, IAA, essential nutrients (Mg, Fe, and K), grain weight and nitrogen content. Overall, co-inoculation with <i>S. maltophilia</i> and <i>R. leguminosarum</i> bv. <i>phaseoli</i> significantly improved salinity tolerance, particularly in the Almas cultivar, through enhanced nutrient uptake, maintenance of membrane integrity, and regulation of hormonal balance.</p>