The π-acidity of anionic malonate-derived N-heterocyclic carbenes (maloNHC)–, [1]–, has been determined experimentally by recording the 77Se NMR chemical shifts of the corresponding maloNHC·Se adducts. Though anionic in nature, [1]– displays a significant π-accepting character, which can additionally be fine-tuned depending on the nature of the counter-cation. The π-acidity of neutral maloNHC-derived carbenes was also assessed by neutralization of the malonate backbone, and it was shown to increase upon O-methylation, giving rise to the (amino)(acrylamido)carbene 1Me and to increase even more dramatically upon protonation of the central carbon atom, which formally generates the diamidocarbene 1H.