The properties of microalgae as bioresources for biodiesel production can be improved by adding nitrogen sources into the culture medium. Thus, Nannochloropsis oceanica CCAP 849/10 was cultured in f/2 media supplemented with five different forms of nitrogen at 0.88 mmol-N l^-1 each: ammonium bicarbonate (NH₄HCO₃), ammonium sulfate ((NH₄)₂SO₄), sodium nitrate (NaNO₃), ammonium nitrate (NH₄NO₃), and urea. The cell density, lipid content, and fatty acid profile of the microalga were determined after 15 days of cultivation. The growth of N. oceanica based on cell number was lowest in the medium with NH₄NO₃, and increased significantly in the medium with NH₄HCO₃. Cells treated with (NH₄)₂SO₄, and NH₄NO₃ produced the highest total lipid contents (i.e., 65% and 62% by dry weight, respectively). The fatty acid profiles of the microalga were significantly different in the various nitrogen sources. The major fatty acids detected in cultures supplemented with NH₄HCO₃, (NH₄)₂SO₄, NH₄NO₃, or urea were C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C20:5, and C22:6. However, the C16:1 content in the NaNO₃-supplemented culture was very low. This study highlights that the nitrogen source can strongly influence lipid production in N. oceanica and its fatty acid composition.