With increasing interest in the potential effects of n-6 and n-3 fatty acids in early life, there is a need for data on the dietary intake of polyunsaturated fatty acids (PUFA) in low-income countries. This review compiles information on the content in breast milk and in foods that are important in the diets of low-income countries from the few studies available. We also estimate the availability of fat and fatty acids in 13 low-income and middle-income countries based on national food balance sheets from the United Nations' Food and Agriculture Organization Statistical Database (FOASTAT). Breast milk docosahexaenoic acid content is very low in populations living mainly on a plant-based diet, but higher in fish-eating countries. Per capita supply of fat and n-3 fatty acids increases markedly with increasing gross domestic product (GDP). In most of the 13 countries, 70–80% of the supply of PUFA comes from cereals and vegetable oils, some of which have very low α-linolenic acid (ALA) content. The total n-3 fatty acid supply is below or close to the lower end of the recommended intake range [0.4%E (percentage of energy supply)] for infants and young children, and below the minimum recommended level (0.5%E) for pregnant and lactating women in the nine countries with the lowest GDP. Fish is important as a source of long-chain n-3 fatty acids, but intake is low in many countries. The supply of n-3 fatty acids can be increased by using vegetable oils with higher ALA content (e.g. soybean or rapeseed oil) and by increasing fish production (e.g. through fish farming).