The content of triacylglycerols (TAG) in krill oil is generally omitted from the labels of commercial supplements and unacknowledged in studies aimed at proving its health benefits. The present study demonstrates that TAG compounds, in addition to phospholipids and lysophospholipids, are an important lipid class in pure krill oil. The fatty acid composition of TAG molecules from krill oil and their distribution on the backbone of TAG structures were determined by gas chromatography and liquid chromatography tandem mass spectrometric, respectively. The content of omega 3 polyunsaturated fatty acids (n-3 PUFA) was similar to those reported in the literature for fish oil. It was estimated that 21 % of n-3 PUFA were at the sn-2 position of TAG structures. To our knowledge, this is the first determination and structural characterization of TAG in pure krill oil supplements.