The marine diatom Thalassiosira pseudonana grown under air (0.04% CO2) and 1 and 5% CO2 concentrations was evaluated to determine its potential for CO2 mitigation coupled with biodiesel production. Results indicated that the diatom cultures grown at 1 and 5% CO2 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 CO2 resulted in higher cell volume and pigment content per cell of T. pseudonana. Interestingly, lipid content doubled when air was enriched with 1-5% CO2. 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 CO2 levels. These results suggested that T. pseudonana seems to be an ideal candidate for biodiesel production using flue gases.