The pervasive presence of microplastics (MPs, <5 mm) and nanoplastics (NPs, <100 nm) in agricultural systems poses significant risks to crop productivity, food security, and human-animal health. The terrestrial environments—where plastic contamination is substantially higher—remain understudied, particularly in the context of crop systems. This chapter synthesizes current knowledge on the uptake, translocation, and phytotoxic effects of micro-nanoplastics (MNPs) in crops, emphasizing the interplay of particle characteristics (size, polymer type, surface charge, and dose), crop species, developmental stages, and environmental exposure pathways. Smaller NPs (e.g. ≤100 nm) exhibit greater bioavailability, infiltrating roots via apoplastic transport, endocytosis, or crack-entry modes, while foliar uptake occurs through stomata and trichomes. Analytical challenges, such as organic matrix interference during digestion, limitations in spectroscopic resolution (e.g. Fourier transform infrared spectroscopy (FTIR), Raman), and difficulties in distinguishing smaller MPs and NPs from natural particles, hinder accurate quantification. Advanced techniques, including pyrolysis gas chromatography-mass spectrometry (Py-GC/MS), inductively coupled plasma mass spectrometry (ICP-MS), and synchrotron-based imaging, show promise but require standardization, and the information obtained is incomparable to existing data where mostly numbers are reported instead of mass. The toxicity is size dependent, and these techniques lack the capability to provide any size information. Mechanistic studies reveal species-specific responses: dicots (e.g. lettuce, carrot) and certain legumes (e.g. cowpea) accumulate NPs more readily than monocots (e.g. wheat, maize), with polymer-dependent toxicity observed for poly(vinyl chloride) (PVC), polyethene (PE), and polystyrene (PS). Critical gaps persist in understanding real-world NP interactions with aged/weathered plastics, multi-contaminant effects, and long-term ecological impacts. The absence of harmonized protocols and field-validated risk assessments limits regulatory frameworks. This chapter underscores the urgency of interdisciplinary efforts to refine detection methodologies, elucidate translocation mechanisms, and evaluate food chain contamination risks, thereby informing strategies to mitigate plastic pollution in agroecosystems.