2H-Pyridazino[1,2-a]indazole-1,6,9(11H)-triones were synthesized through one-pot, three-component condesation of aldehydes, maleic hydrazide, and dimedone using a green and inexpensive Bronsted acidic ionic liquid 1-methyl-2-pyrrolidinone hydrosulfate ([Hnmp]HSO4) as catalyst under solvent-free conditions. The method provided several advantages such as milder conditions, shorter reaction time, high yields, and environmentally benign procedure.