Plant hormones, known as phytohormones, are crucial in regulating plant growth, development, and responses to environmental stress. Traditional methods for detecting and monitoring these molecules are often slow, complex, and unsuitable for real-time applications. Nanobiosensors provide a game-changing solution, offering enhanced sensitivity, specificity, and the ability to perform real-time, on-site monitoring of phytohormones. This chapter focuses on the fusion of nanotechnology and biosensing to detect key plant hormones, including auxins, gibberellins, cytokinins, abscisic acid, and ethylene. It delves into the design strategies, materials, and functionalization methods used in developing nanobiosensors, explaining how these sensors interact with specific hormones. Key advances in nanomaterials, such as carbon nanotubes, quantum dots, and nanoparticles, are highlighted for their role in boosting detection accuracy and signal transmission. The chapter also explores the practical applications of nanobiosensors in agriculture, including precision farming, stress monitoring, and crop enhancement. Challenges such as sensor stability, selectivity in complex environments, and scalability are also addressed. Finally, the chapter offers a forward-looking view on improving nanobiosensor technology and its potential to promote sustainable agriculture and ensure food security.