A mild and general protocol involving amnio- and oxyselenation of diverse alkenes for the efficient synthesis of organo-Se compounds is achieved via an environmentally benign calcium-catalyzed three-component reaction. This selenofunctionalization reaction exhibits excellent substrate/functional group tolerance and high levels of chemo- and regioselectivity. Its utility was exemplified in the late-stage functionalization and even aggregation-induced emission luminogen labeling of organo-Se compounds.