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The current study focused on enumerating the potential plant growth-promoting rhizobacteria (PGPR) from the rhizosphere of <i>Arachis hypogaea</i> L. Among the several colonies grown on an Ashby plate, only seven isolates (Ah1 to Ah7) had nitrogen-fixing potential. The Ah4 isolate showed higher potential for plant growth-promoting (PGP) activities than the other isolates. This isolate was recognized as <i>Kosakonia</i> sp. MGR1 through 16S rRNA sequencing with 99.7% similarity to nitrogen-fixing <i>Kosakonia</i> genus and 61% match with <i>K. cowanii</i> in phylogenetic tree analysis. <i>Kosakonia</i> sp. MGR1 had the potential to produce an excellent quantity (26.17 µg·mL⁻¹) of indole-3-acetic acid (IAA) in 6% tryptophan-enriched media than the other concentrations (2%, 4%, 8%, and 10%). Additionally, it contained remarkable phosphate-solubilizing efficiency of tricalcium phosphate (29.3 µg·mL⁻¹) in 5 days of incubation. The growth conditions of <i>Kosakonia</i> sp. were optimized as 35 °C, pH 7.5, and 48 h of incubation with glucose. The isolate MGR1 produced 96.35 ± 3.45, 89.6 ± 5.61, and 99.21 ± 5.24 µg·mL⁻¹ of IAA, nitrogen, and soluble phosphate, respectively. Furthermore, <i>Kosakonia</i> sp. MGR1 had the potential to enhance the growth and biomolecule contents of <i>A. hypogaea</i> L. The results concluded that <i>Kosakonia</i> had admirable PGP activities; hence, it showed a significant impact on the active growth and biomolecules of <i>A. hypogaea</i> L.