Hexagonal boron nitride (hBN)-based nanomaterials stand out as promising materials with many excellent physicochemical, mechanical, and biological properties. The super high specific surface area, thermal and chemical stability, and other unique properties enable exceptional environmental capabilities. This review comprehensively presents the latest advances in the use of hBN-based nanomaterials for a number of environmental and energy applications, including adsorption, photocatalysis, membrane separation, disinfection, environmental sensing, as well as energy conversion and storage. Properties and structures of hBN nanomaterials and their synthesis and modification methods are summarized. The unique properties of hBN-based nanomaterials enabling exceptional environmental capabilities are emphasized. The toxicity and recyclability of hBN-based nanomaterials are considered. Research needs for future environmental applications of hBN-based nanomaterials are discussed.