This review explores the efficacy of nanomaterials as sustainable alternatives to conventional subgrade soil stabilizers, driven by advancements in nanotechnology over the past two decades. It examines the impact of various nanoparticles on key soil engineering properties, including compaction, California Bearing Ratio (CBR), compressive and shear strength, and swelling-shrinking behaviour. The study also analyzes nanoparticle-soil interactions at micro and nano scales, highlighting their role as primary additives or secondary activators in enhancing soil strength and stiffness. Ecological and geo-environmental concerns associated with nanoparticle use are critically reviewed, alongside potential future research avenues. Findings indicate that nanoparticles significantly improve subgrade mechanical properties, reduce settlement, and absorb heavy metal pollution while maintaining pH balance. Their filling capacity and gel formation enhance bonds, adhesion, and friction angles, with effectiveness varying by nanoparticle type, dosage, and soil characteristics. This study offers valuable insights into eco-friendly nanoparticle applications in road engineering.