High photosynthetic rates and high lipid content make microalgae a promising source for the industrial production of edible oils. Enhancement of oleic acid production in microalgae is an important area in the algae-based edible oils research. This study employed the mixotrophic mode of nutrition with a nutrient-rich growth phase (GP) followed by two different stress phases (SPs), including nitrate depletion (single stress phase; SSP) and nitrate depletion with salinity (dual stress phase; DSP). In DSP, higher oleic acid (C18:1) content was observed and considered the same for autotrophic mode. In addition to DSP, it evaluated the role of nitrate to phosphate ratio in GP towards fatty acid biosynthesis. The relative and absolute quantities of fatty acids were measured in mixotrophic and autotrophic cultivations. Higher oleic acid was obtained at 250 mM NaCl DSP condition in mixotrophic cultivation compared to other conditions. Whereas autotrophic mode microalgae cultivated in dual stress phase (DSP for A-GP-1N1P, DSP for A-GP-1N2P, DSP for A-GP-1N4P, and DSP for A-GP-1N6P) resulted in ~30 % (w/w) of total fatty acids with 55 % of Oleic acid in absolute quantity. Overall, the study depicted a distinct influence of nitrate, nitrate to phosphate ratio, nitrate depletion (single stress), and dual stress on the oleic acid yield. The application of dual stress to microalgae cultivation is a new approach to oleic acid enhancement. • Nitrate depletion and salinity in stress phase influenced oleic acid biosynthesis. • Study achieved 30 % of total fatty acids with 55 % of Oleic acid in absolute quantity. • Nitrates and phosphates in growth phase also influenced fatty acids production. • Nitrates increment in mixotrophic growth phase negligibly affected oleogenesis. • Biosynthesis of fatty acids is interdependent with growth phase and stress phase.