The present disclosure provides a method for preparing a selective catalytic reduction (SCR) catalyst, the SCR catalyst comprises a metal ion-exchanged zeolite. A method uses an in-situ ion exchange process. A process includes admixing a zeolite in the ammonium (NH4+) form with an aqueous mixture comprising water, a transition metal ion source, and, optionally, an acid, to form a slurry containing a metal ion-exchanged zeolite.