The swift emergence of nanotechnology in agricultureAgriculture has brought considerable benefits through engineered nanoparticles (ENPs), which have increased crop production, improved nutrient absorption, and reduced pest resistance. With enhanced exposureExposure to engineered nanoparticles comes the potential for toxicity, more accurately referred to as nanotoxicity, associated with the reactions of plants exposed to nanomaterialsNanomaterials (NMs). Knowing how plants detect, respond, and mitigate their exposure to nanoparticle-induced stress is needed for their responsible and sustainable utilization in agriculture. The exposure of plants to many nanoparticles can induce oxidative stress because of more reactive oxygen species (ROS) accumulation. This imbalance of ROS damages the cellular structures composed of lipids, proteins, and nucleic acids, ultimately inhibiting growth and altering plant physiology. To balance excess oxidative stress, plants also activate subsequent detoxification mechanisms to reduce ROS levels. Antioxidant enzymes like catalase, superoxide dismutase (SOD), and peroxidases are the part detoxification mechanisms. Molecular regulation, beyond antioxidant responses, also includes signal transduction pathways controlled by mitogen-activated protein kinases (MAPKs), stress-responsive transcription factors including WRKY, DREB, NAC, and hormonal signaling networks involving abscisic acid, ethylene, jasmonic acid, and salicylic acid to modulate the expression of defence-related genes, increase cell wall integrity, and increase repair processes. This chapter discusses and summarizes all these molecular processes happening in plants after the exposure to the nanomaterials.