Chia mucilage is formed by the hydration of chia seeds and presents characteristics that potentiate its application as substitute of fat in several foods. In this study, mayonnaises were prepared with different levels of freeze-dried chia mucilage instead of oil or egg yolk. The substitution of oil in mayonnaise promoted increased stability and texture parameters, and the mayonnaise substituted by egg yolk presented similar stability and texture parameters as the control mayonnaise. The substitution of oil in mayonnaise was about 50% with 45% oil substitution, whereas for the mayonnaise with 35% of egg yolk replacement it was about 0.94%. Sensorially, an inverse relation was found, the mayonnaises with substitution of the egg yolk that presented a smaller reduction of the lipid content, presented better sensory acceptance than the mayonnaise with substitution of the oil. Therefore, the results indicated that chia mucilage has potential to substitute part of the amount of oil in the mayonnaise formulation. As for the use of the mucilage in the substitution of the egg yolk, it is not possible to promote a significant reduction in the lipid content nor maintain emulsion stability.Keywords: chia seed, emulsion, fat replacement, sensory analysis, technological properties Practical Application: Chia mucilage presents high emulsifying hability and water-holding capacity that potentiabilize its use as a substitute for fat in various foods. Mayonnaises developed with up to 45% oil substitution by chia mucilage, presented a reduction in the lipid content by about 50%, an increasing stability and a good sensorial acceptance.