Drought stress mitigation may involve multiple strategies that engage plants physiologically, one of which is the application of beneficial rhizobacteria that enhance plant tolerance. This study aimed to assess the ability of phosphate-solubilizing bacteria (PSB) to improve the growth and physiology of Achillea santolina (Santalin yarrow) under drought stress. The interaction effects of PSB (Pseudomonas fluorescens isolates FRPF4, FRPF6, and FRPF12) (at 107 CFU mL^-1) and drought stress (30, 50, and 80% field capacity) appeared in a factorial test based on a completely randomized design located in a greenhouse (n=3; P<0.05). Several vegetative and physiological parameters came under study at full flowering. Measurable growth factors were plant shoot height, canopy diameter, root length, and fresh and dry weights. The results revealed a significant decrease in all growth parameters under drought stress. However, PSB isolates, especially FRPF4, significantly mitigated the adverse effects of stress on vegetative factors. Drought stress significantly affected the leaf samples by increasing their total soluble sugars (TSS), free proline, total flavonoids (TF), and DPPH contents. Drought-stressed plants inoculated with the PSB isolates showed a significant decrease in free proline and DPPH concentrations. However, the TSS and TF contents increased in the stressed plants treated with PSB isolates. Carotenoid, chlorophyll a, b, and total chlorophyll contents also decreased in the stressed plants. However, these factors increased in plants treated with PSB isolates in response to water-deficit stress. Thus, PSB isolates may mitigate the adverse effects of drought stress on Santalin yarrow plants through several direct and indirect mechanisms.