The present study aimed to isolate and evaluate a local Protosiphon sp. ‎for biodiesel production and‏ ‏antioxidant activity of its residual lipid-free ‎biomass. Phylogenetic analysis confirmed that the isolate is‏ ‏Protosiphon ‎botryoides. In the control medium using 250 mg L-1 NaNO3 as a nitrogen ‎source, cells‏ ‏showed 37.7 dw% lipid content at stationary phase. At ‎different nitrogen levels, increasing of nitrogen‏ ‏concentration resulted in ‎obvious increase in growth, showing the maximum biomass productivity ‎of‏ ‏‎0.133 g L-1d-1at middle exponential phase using 750 mg L_1 NaNO3, ‎with simultaneous reduction in lipid content, reaching its lowest recorded ‎value of 27.9 dw%. Due to enhancement of lipid content of N deficient‏ ‏culture (125 mg L‏-‏‎1 NaNO3), it showed the highest lipid productivity of ‎‎41.3 mg L-1d-1. Fatty‎‏ ‏acid analysis confirmed the dominance of linoleic ‎acid, eicosatrienoic acid, oleic acid, and palmitic acid.‎‏ ‏Biodiesel ‎characteristics complied with the international standards and showed ‎better properties than‏ ‏some other reported biodiesel promising ‎microalgae. In addition, lipid-free biomass showed high radical‏ ‏scavenging activity of 55.3%, which confirms its suitability as additional ‎nutritional and pharmaceutical‏ ‏material for enhanced biomass ‎valorization.‎