© 2022 International Phycological Society.The present study aimed to optimize the light intensity coupled with different salinity regimes for enhanced growth and antioxidant properties of the brown seaweed Gongolaria barbata. Five experimental trials (T1–T5) were suggested using response surface methodology, where growth rate and antioxidant properties of G. barbata were evaluated in each run at the end of the experiment. The model for growth rate showed differences not statistically significant among all studied groups. However, concentration of methanol extract needed to scavenge 50% of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (IC50), total phenolics, total flavonoids, total carotenoids, chlorophyll a and chlorophyll c showed significant differences among the five studied groups. Total phenolic and flavonoid contents were primarily affected by light, showing the highest values of 2.08 mg gallic acid equivalent g−1 and 2.41 mg rutin g−1 at 50 µmol photon m−2 s−1. However, salinity stress showed a more pronounced impact on pigments. DPPH scavenging activity was influenced by the concentration of other compounds, which showed a significant increase by 34% in group T4. The present study recommended light intensity of 53.86 µmol photons m−2 s−1 at 24.02‰ salinity as the optimum conditions to achieve the maximum antioxidant activity along with phenolic and flavonoid contents (desirability = 0.82), without significant impact on the growth.