Inwardly rectifying potassium channels require binding of phosphatidylinositol‐4,5‐bisphosphate (PIP₂) for channel activity. Three independent sites (aa 175–206, aa 207–246, aa 324–365) were located in the C‐terminal domain of Kir2.1 channels by assaying the binding of overlapping fragments to PIP₂ containing liposomes. Mutations in the first site, which abolished channel activity, reduced PIP₂ binding of this fragment but not of the complete C‐terminus. Point mutations in the third site also reduced both, channel activity and PIP₂ binding of this segment. The relevance of the third PIP₂ binding site provides a basis for the understanding of constitutively active Kir2 channels.