The objective of this study was to evaluate the effects of irradiance levels and spectra produced by solid-state light-emitting diodes (LEDs) on carotenoid content and composition changes in Brassicaceae microgreens. A system of five high-power, solid-state lighting modules with standard 447-, 638-, 665-, and 731-nm LEDs was used in the experiments. Two experiments were performed: (1) evaluation of LED irradiance levels of 545, 440, 330, 220, and 110 μmol m⁻² s⁻¹ photosynthetically active flux density (PPFD) and (2) evaluation of the effects of 520-, 595-, and 622-nm LEDs supplemental to the standard set of LEDs. Concentrations of various carotenoids in red pak choi and tatsoi were higher under illumination of 330–440 μmol m⁻² s⁻¹ and at 110–220 μmol m⁻² s⁻¹ in mustard. All supplemental wavelengths increased total carotenoid content in mustard but decreased it in red pak choi. Carotenoid content increased in tatsoi under supplemental yellow light.