Abstract: Carboxyl-functionalized poly(ionic liquid) (CFPIL) was easily synthesized from its starting material and characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis and elemental analysis. The synthesized CFPIL was used as an efficient heterogeneous catalyst for the synthesis of β-amino ketones by three-component one-pot Mannich reaction between various aromatic aldehydes with amines and acetophenone at room temperature under solvent-free condition. The effect of the amount of catalyst and reaction time were investigated. The results showed that CFPIL has good to moderate catalytic activity and reusability. The catalytic process was simple and the catalyst could be easily recovered by filtration and washed with ethanol to reuse for the next experiment without significant loss of catalytic activity. Graphical Abstract: [Figure not available: see fulltext.]. © 2017, Springer Science+Business Media B.V.