In recent days, foods rich in nutraceuticals are in demand because of their nature to prevent or heal several chronic diseases. Efficiency of nutraceuticals is usually challenged due to its poor bioavailability, safety, and toxicity-related issues. The major concerns of nutraceutical’s bioefficiency is the bioavailability of the nutraceuticals, which includes endogenous factors at different stages of the gastrointestinal tract (mouth, stomach, and intestine), physicochemical and enzymatic reactions involved in that, release of nutraceuticals from the food matrices or nanocarriers in gastrointestinal fluids, solubility of the nutraceuticals, their interaction with other components of the gastrointestinal tract, absorption of nutraceuticals by the epithelial layer, and the chemical and biochemical transformations into epithelial cells. Exogenous factors affecting the bioavailability are physicochemical properties of the food sample, their food matrix, processing, and storage of the food materials. Bioaccessibility or bioavailability assessment of nutraceuticals can be assessed by in vitro, in vivo, in situ, and ex situ methods. Assessment of bioaccessibility or bioavailability of different nutraceuticals like carotenoids, polyphenols, glucosinolates, and vitamin E have been done in different food matrices and shows wide variation. Among them, the percentage bioavailability of polyphenols is comparatively better. To improve the bioavailability of these nutraceuticals nanotechnology is applied, which enhances nutraceutical delivery systems through formulation of nanoemulsion, nanoliposomes, solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), and polymer nanoparticles.