Immunoassays in food and feed analysis enable the detection and quantification of various analytes such as food allergens, gluten, mycotoxins, bacterial toxins, antibiotics, hormones, anabolic steroids, and vitamins. These analytes are measured across a wide concentration range, from milligrams to nanograms per kilogram. The importance of considering interferences from different matrices in food and feed bioanalytics is discussed, including influences of raw ingredients and processed products. Legal regulations and maximum residue limits for certain analytes, particularly within the European Union, are reviewed. The chapter also emphasizes the significance of representative sampling and the challenges associated with it. The validation and verification processes required for immunoassays, especially in the context of ISO 17025 accreditation, are considered. The necessity of confirmatory methods, such as LC-MS/MS, to validate the results obtained from ELISA screening methods is discussed.