<p>This study evaluated the combined effects of light quality (white, blue, red, and green) and phytohormones (indole-3-acetic acid/IAA, gibberellic acid/GA₃ and salicylic acid/SA) on the growth and biochemical composition of <i>Dunaliella salina</i> using artificial seawater (ASW) and wastewater (WW) culture media. The maximum fresh weight in ASW was achieved under white and red light, whereas in WW cultures blue and red light was superior. Red light with GA₃ and IAA showed the greatest synergy in terms of fresh weight increase. Dry weight followed similar trends, with the red-IAA combination yielding the highest value, suggesting the crucial role of red light in biomass production when combined with IAA. The highest amounts of chlorophyll <i>a, b</i>, and carotenoids were observed in SA treatment and under red, blue, and green light irradiation, respectively. Green light elicited maximal protein content in WW cultures, whereas the highest concentration of soluble sugars was achieved under red light supplemented with IAA. Glycerol accumulation was highest in WW-GA₃ treatment under white light. One of the significant results of this study is the synergistic effect of red light with IAA in increasing biomass and carbohydrates and with SA in increasing carotenoids. Another finding of this research is the significant increase in protein in algae grown under green light. This study offers valuable insights for the development of sustainable microalgal cultivation systems that use wastewater resources and light-hormone combinations.</p> Graphical abstract <p></p>