Naphthyridines, also known as diazanaphthalenes, are a group of heterocyclic compounds that include six isomeric bicyclic systems containing two pyridine rings. 1,6-Naphthyridines are one of the members of such a family capable of providing ligands for several receptors in the body. Among such structures, 1,6-naphthyridin-2(1H)-ones (7) are a subfamily that includes more than 17,000 compounds (with a single or double bond between C3 and C4) included in more than 1000 references (most of them patents). This review will cover the analysis of the diversity of the substituents present at positions N1, C3, C4, C5, C7, and C8 of 1,6-naphthyridin-2(1H)-ones, the synthetic methods used for their synthesis (both starting from a preformed pyridine or pyridone ring), and the biomedical applications of such compounds.