<p>Inorganic fertilizer use poses environmental and health concerns despite the increased yields in commercial agriculture. <i>Gliricidia sepium</i> is a versatile plant in organic agriculture. Organic manure lacks sufficient amounts of readily available nutrients for plants. This study was conducted to determine the effect of two bacterial strains from Sri Lanka on enhancing the quantity and nutrient content of <i>Gliricidia sepium</i> for efficient utilization in sustainable agriculture. Two isolates I–I and I–II were partially identified based on rDNA and <i>gyrA</i> genes as <i>Bacillus</i> spp. and a phylogenetic tree was built. Plant growth-promoting attributes of phosphorus solubilization ability, Indole acetic acid production (IAA), and catalase activity were determined under laboratory conditions. A greenhouse experiment was conducted with <i>Gliricidia sepium</i> stem cuttings inoculated with two strains. Plant growth-promoting characters and nutrient contents in dry leaves were determined. The two strains were partially identified as <i>Bacillus</i> spp. with phosphorus solubilizing ability mainly. Plants inoculated with both strains enhanced plant height, leaf number, internodal length, SPAD values, root length, and dry shoot and root weights in contrast to control plants. Nodule formation was positively affected in inoculated plants. Nitrogen, phosphorus, and potassium levels in dry leaves, as well as nitrogen levels in pot soil, significantly increased in inoculated plants. Our findings concluded that the positive effect of two strains on <i>Gliricidia sepium</i>, which sheds light on their application in sustainable agriculture.</p>