The photophysics and photochemistry of a series of naphthoxazinones have been studied using a combination of methods ranging from steady-state and time-resolved spectroscopic techniques to product analysis. The photophysics of naphthoxazinone derivatives is very dependent on the structure: phenanthrene-like compounds exhibit higher fluorescence quantum yield than the less aromatic anthracene-like homologous. The latter, exhibit a substantial degree of charge transfer in the excited singlet state. These compounds are fairly photostable in the absence of additives, yielding a single photoproduct arising from the triplet state. The presence of electron donors such as amines increases the photoconsumption quantum yield and changes the product distribution, the primary photoproduct being a dihydronaphthoxazinone that photoreacts further yielding ultimately an oxazoline derivative.