The synthesis of sulfonamidylated polycyclic quinazolinones was developed via visible-light-induced cascade N-centered radical addition/cyclization of unactivated alkenes using 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as the photocatalyst. The easily accessible N-sulfonylaminopyridinium salts were employed as N-centered radical sources. This transformation has the advantages of operational simplicity, good functional group compatibility, broad substrate scope and mild conditions, affording a variety of sulfonamidylated pyrrolo- and piperidino-quinazolinones in yields up to 91%.