A straightforward synthetic strategy to construct biologically relevant phenanthridinones and quinolinones was developed via visible-light-promoted direct oxidative C-H amidation. In this photocatalytic system, amidyl radicals can be generated by homolysis of the N-H bond of simple amide precursors via single-electron transfer under blue LED illumination, which leads to oxidative intramolecular C-H amidation. Moreover, an efficient synthetic strategy using a photocascade enabled facile assembly of quinolinone structures through a catalytic sequence involving triplet energy (ET) transfer-based E/Z olefin isomerization and subsequent photocatalytic generation of amidyl radical intermediates.