Dihydro[1,3]oxazines are an important class of heterocyclic compounds having a wide range of biological and material properties. Medicinally, they possess diverse pharmacological activities, such as bactericidal, fungicidal, microbiocidal, antitumor, anti-HIV, and anti-inflammatory agents. Apart from being biologically active, they are materially useful for making polybenzoxazines. Polybenzoxazines are a novel class of non-conjugated thermosetting materials that belong to the family of addition-curable phenolic resins. They have lucrative properties such as small shrinkage in curing, low water absorption, good thermal stability, and there is no release of volatile materials during cure, and no need for catalyst and inexpensive raw materials. Further, the flexibility in designing a monomer gives polybenzoxazines an additional edge over ordinary phenolic resins. This review briefly describes the syntheses, including eco-friendly strategies, and biological and material significance of various dihydro[1,3]oxazine derivatives.