An unprecedented copper and in situ-generated triflic acid relay-promoted four-component cascade reaction of cyanamides, diaryliodonium triflates, propargylic amines, and H2O was established for rapid and concise construction of diverse five-membered cycloguanidines. Copper-catalyzed guanidination/intramolecular hydroamination and in situ-generated HOTf-accelerated hydration proceeded sequentially with high level of chemoselectivity and regioselectivity, and six new bonds were simultaneously built in high yields. Thus, diaryliodonium triflates served not only as an arylation reagent but also as an internal acid promoter, establishing an alternative strategy for highly efficient utilization of diaryliodonium trifates.