Borocarbonitride (BCN) is a new type of photocatalyst, but bulk BCN shows a large band gap, and low surface area, and moderate activity for photocatalysis. Here, a three‐dimensional (3D) porous ceramic BCN aerogel was developed as an effective photocatalyst for relevant reactions. The unique structures endow the aerogel with an adjustable band gap and a high surface area, excellent stability, and improved crystallinity, which accelerates the separation and transfer of electron‐hole pairs and promotes catalytic kinetics, thus enhancing the performance of photocatalytic reactions for hydrogen generation and carbon dioxide reduction. This work supplies a low‐cost, convenient and green synthesis method for building ceramic aerogels, and it provides a simple colloid chemistry strategy combined with boron‐containing compounds to facilitate further innovative breakthroughs in the novel ceramic aerogel materials design and development in the field of catalysis.