Purpose <p>Soil degradation and declining productivity remain challenges in sustainable agriculture. Plant growth-promoting rhizobacteria (PGPRs) are a crucial tool for enhancing nutrient levels in plants, contributing to sustainable agriculture. To further improve plant growth and soil properties, biochar is identified as an effective material and a supportive medium for protecting PGPRs.</p> Methods <p>This study investigates the synergistic effect of endophytic (<i>Bacillus sp.</i>) and rhizospheric (<i>Proteus sp.</i>) bacteria, in combination with varying concentrations of biochar (5% and 10%), on the growth of cucumber (<i>Cucumis sativus</i> L). A pot experiment was conducted with treatments including biochar, PGPR inoculation, and their combinations alongside a control to assess their impact on different plant growth parameters and nutrient uptake.</p> Results <p>The combined treatment of PGPR and biochar significantly enhanced plant growth, biomass accumulation, chlorophyll content and relative water status compared to individual treatments. Among all treatments, the combination of endophytic bacteria with 5% biochar showed the improvement in plant performance. This treatment also promotes total soluble sugar by up to 1.93-fold and rhizospheric bacterial colonization by 4.24-fold. Soil analysis revealed marked improvements in nutrient availability, including phosphorus (2.12-fold), potassium (1.39-fold), iron (2.74-fold), zinc (6.97-fold) and sulfur (2.34-fold) relative to the control, highlighting enhanced soil fertility. In contrast, higher biochar concentration (10%) showed comparatively reduced effectiveness, suggesting a dose-dependent response.</p> Conclusion <p>Overall, the findings demonstrate that the synergistic application of biochar with beneficial microbes significantly promotes cucumber plant growth and soil health. This nature-based solution offers a sustainable and effective approach for enhancing crop productivity and soil health.</p>