RNA decoys are exogenous molecules that have a sequence matching the natural RNA target of an RNA binding protein. Usually the RNA binding protein binds to its natural target, but when the RNA decoy is introduced into the cell then it binds some of the RNA binding protein. If enough of the decoy is in the cell, the RNA binding protein is mostly attached to the decoy and some of its natural RNA target is left unbound. This essentially "flips a switch" in the cell, as the process affected by the RNA binding protein-RNA interaction goes from its bound state to its unbound state.

For example, if the RNA binding protein directs the splicosome to remove a particular exon, tying up that protein with an RNA decoy would cause production of a mature mRNA that contains the exon of interest (because the absence of bound RNA binding protein on its RNA target caused the splicosome to proceed differently with splicing).