Bioavailability is defined as “the fraction of an ingested nutrient that is available for utilization in normal physiological functions or for storage”. Available studies on carotenoids bioavailability are based on the measurement of their levels in serum or plasma. Dietary components were reported to affect the rate of carotenoids absorption. On digestion, carotenoids are incorporated into the lipid phase and then are emulsified into small lipid droplets. The nature and amount of lipids in the diet greatly affect the emulsification, secretion of bile salts, and formation of mixed micelles all of which are currently important subjects to understand the carotenoids bioavailability. Specific lipids, vegetable oils and their fatty acid moiety have been shown to affect the mixed micelles formation that positively influences the absorption of carotenoids. Gavages and dietary studies revealed that oleic acid micelles and olive oil (oleic acid, C18:1) enhance the intestinal accessibility of carotenoids more than linoleic acid micelles or vegetables oils rich in polyunsaturated fatty acids (PUFA). The chemistry of fats or oils which may act differently at various stages of absorption and metabolism of carotenoids is discussed. This review shows that dietary unsaturated fat appears to be a suitable carrier for carotenoids when oxidative stress is a critical issue in nutrition-related degenerative disorders.