Global warming is one of the main problems that poultry industry is currently facing, since high temperatures could generate oxidative stress and impact on nutritional quality of its derived products. The aim of this work was to study the effects of dietary supplementation with polyphenols from defatted chia seed cake on the fatty acids composition of eggs from Japanese quail exposed to heat stress. A total of 24 females were randomly assigned into different groups (n=12 per group) according to whether they were fed with standard commercial diet (BASAL) or chia polyphenol supplemented diet (500 mg polyphenol/Kg or CP500). Half of the animals in each diet group were exposed to 34 °C for 9 hours a day (Heat Stress or HS groups). After 23 days of experimental conditions eggs were collected, and lipids from yolks were extracted. Fatty acid composition (saturated, monounsaturated and polyunsaturated fatty acids or SFA, MUFA and PUFA respectively) was analyzed by gas chromatography. Egg yolks of HS-BASAL animals showed higher proportion of C12:0, C13:0 and C20:0, but with no significant differences in ΣSFA respect to those animals that had no heat stress and the same basal diet (NHS-BASAL). Besides, ΣMUFA decreased in HS-BASAL animals (mainly due to the reduction in C18:1 content), and no significant differences were observed in ΣPUFA. Regarding the effect of polyphenols, CP500 helped to decrease ΣSFA and produced an increment of ΣPUFA (specifically C18:3, C20:4, C20:5 and C22:4) respect to BASAL diet in heat stress conditions. In conclusion, the use of defatted chia seed cake seems to be a promising sustainable strategy to improve the nutritional quality of eggs from heat-stressed Japanese quail.