The marine diatom Thalassiosira pseudonana grown under air (0.04% CO 2 ) and 1 and 5% CO 2 concentrations was evaluated to determine its potential for CO 2 mitigation coupled with biodiesel production. Results indicated that the diatom cultures grown at 1 and 5% CO 2 showed higher growth rates (1.14 and 1.29 div day −1 , respectively) and biomass productivities (44 and 48 mg AFDW L −1  day −1 ) than air grown cultures (with 1.13 div day −1 and 26 mg AFDW L −1  day −1 ). The increase of CO 2 resulted in higher cell volume and pigment content per cell of T . pseudonana . Interestingly, lipid content doubled when air was enriched with 1–5% CO 2 . Moreover, the analysis of the fatty acid composition of T . pseudonana revealed the predominance of monounsaturated acids (palmitoleic-16:1 and oleic-18:1) and a decrease of the saturated myristic acid-14:0 and polyunsaturated fatty acids under high CO 2 levels. These results suggested that T . pseudonana seems to be an ideal candidate for biodiesel production using flue gases.