The use of biochar in geotechnical and geoenvironmental engineering is relatively underexplored, especially in terms of its effects on soil properties when combined with sugarcane bagasse. This study investigates the impact of biochar derived from sugarcane bagasse on the strength and water retention behavior of low-plasticity clay soil, making a unique contribution to the field. Biochar, a carbon-rich material produced through the pyrolysis of organic biomass, has gained attention for its ability to improve soil properties and address environmental issues. This study incorporated five different percentages of bagasse biochar (0, 1, 2, 3.5, and 5%) into low-plasticity clay soil to create biochar-amended soil specimens. Through unconfined compressive strength and water retention tests. This finding implies that adding biochar improves the soil’s capacity to hold onto moisture, which could be advantageous in geoenvironmental applications to reduce variations in soil moisture and promote plant growth. Additionally, the study shows that adding up to 1% biochar to soil improves its strength characteristics. The presence of biochar altered soil structure, pore distribution, and inter-particle bonding, leading to an increase in strength. In conclusion, biochar amendment offers potential for enhancing soil water retention and strength properties. The use of sugarcane bagasse-derived biochar in low-plasticity clay soil presents promising opportunities for geoenvironmental engineering applications.