Objective To evaluate three flowers of Hibiscus rosa-sinensis (H. rosa-sinensis), Quisqualis indica (Q. indica) and Senna surattensis (S. surattensis) for their antioxidant activity by different methods in addition to total phenolic, flavonoid and pigment contents. Methods Antioxidant activity of water, ethanol and absolute ethanol extracts of three flowers; H. rosa-sinensis, Q. indica and S. surattensis was evaluated. The antioxidant activity was assessed by 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activity, ferrous chelating activity, reducing power, nitric oxide scavenging activity, hydroxyl radical scavenging activity as well as total antioxidant capacity. Total flavonoids, total phenols and total pigments including chlorophylls and carotenoids were measured for the three flowers. Results The results showed that the highest total antioxidant capacity at concentration of 500 mg/L was found in S. surattensis as 0.479 ± 0.001. Scavenging activity of H. rosa-sinensis, Q. indica and S. surattensis flower extracts against 1,1-diphenyl-2-picrylhydrazyl radical showed the highest activity of (90.20 ± 0.29)% with 500 mg/L. Phytochemical screening of the three flowers extracts were carried out for alkaloids, flavonoids, saponins, tannins, steroids, glycosides, terpenoids, amino acid and mucilages. H. rosa-sinensis showed the total phenolic in water extract of (235.77 ± 14.31) mg/100 g, the other two flowers Q. indica and S. surattensis had the total phenolic in ethanol extracts of (937.70 ± 25.06) and (850.30 ± 13.81) mg/100 g, respectively. On the other hand total flavonoids were identified in absolute ethanol extracts in the three flowers [(32.83 ± 1.34), (49.24 ± 4.87) and (2.79 ± 0.23) mg/100 g, respectively]. Conclusions The extracts in the constituents of the three flowers could be used as additives as supplement fractions in foods.