Lactam rings are essential structural motifs in organic chemistry, widely present in natural products and clinically important drugs, such as antibiotics and antiepileptics. Existing methods for synthesizing N-functionalized lactams often require harsh conditions, toxic reagents, or complex catalytic systems. Here, we report a mild and efficient photochemical approach for generating N-centered radicals, enabling straightforward N-heteroarylation of lactams. This versatile method enables the synthesis of a range of N-(het)arylated lactams and is effective even in aqueous media, facilitating the functionalization of biomolecules. Furthermore, the photochemical reaction is easily scalable under continuous flow conditions, making it highly suitable for large-scale applications.