The antioxidant activity of leafy vegetables is an important aspect of its nutritional value. Based on the literature data light is a powerful tool used as a natural factor seeking to alter the antioxidant activity during harvest and may result in prolonged shelf-life. Thus our aim was to determine if the spectral composition affects the antioxidant activity of mustard microgreens at the same light intensity. Mustard microgreens (Brassica juncea) were grown in a peat substrate, in (I) a greenhouse when natural light was supplemented with white light-emitting diodes (LEDs) lighting (16h), and (II) in a controlled-environment chamber (CEC)under R_61%, B_20%, W_15%, and FR_4% spectral composition LED’s. 20±3 °C temperature and total PPFD of 150, 200, and 250 µmol m-²s-¹ were maintained in both treatments. Samples were taken on a harvest day (D₀), one (D₁), and three (D₃) days after harvest and were held in the light or dark at +4°C. Results showed that depending on light spectra, 150 µmol m-²s-¹ resulted in a significant difference in FRAP activity only on D_{3/light and dark} between both treatments. Spectral composition of R_61%, B_20%, W_15%, and FR_4% resulted in higher antioxidant activity than white light under 150 µmol m-²s-¹. At PPFD levels of 200 and 250 µmol m-²s-¹, similar results were found on D₀, D_1/light, and D_{3/ light and dark} when the spectral composition of R_61%, B_20%, W_15%, and FR_4% showed effectuate significantly higher antioxidant activity. It is important to understand how efficiently plants use the light they receive, that kind of knowledge may help to reduce energy costs and impact profitability, and productivity. Our findings show that even separate light components such as PPFD can enable in a higher efficiency. Concluding by manipulating the spectral composition of the light during mustard microgreen growth, antioxidant activity may be altered during storage.