L-Arginine catalysed the Knoevenagel condensations of aromatic, heteroaromatic and α,β-unsaturated aldehydes with malononitrile and acetylacetone to afford α,β-unsaturated nitriles and ketones. The reactions were carried out at room temperature in the ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate. Moderate to excellent yields (45–100%) were achieved. The L-arginine/ionic liquid combination was successfully recycled for five runs without significant loss of activity.