Carbon materials are inexpensive and high‐performance nanomaterials producing ample scope for versatile applications. Graphdiyne (GDY) is a two-dimensional allotrope of carbon having sp and sp² hybridized planar carbon atoms. GDY was firstly synthesized by Li and co-workers in 2010, having diacetylene linkages, conjugated system, wide surface spacing, and pores distribution, tunable electronic properties, good chemical stability, and semiconductor characteristics. In this review, we examine GDY properties, synthesis, bandgap tunability, and current advancement in photocatalytic applications. Recent modifications in electrical, optical, and magnetic properties and some strategies to alter the bandgap of GDY, including applying strain, doping, co-doping, morphology formulation, and heterojunction construction, were elaborated. Different structural morphological analysis, including nanotube, nanowires, nanosheets, nanowalls, and 3D GDY framework, were also discussed. Earlier GDY studies are bound to theoretical analysis as if now their experimental validation has also been reported for feasible photocatalytic applications. The GDY-based nanocomposites were extensively explored for photodegradation, photoreduction of CO₂, photocatalytic hydrogen production. The focus of this review is to provide an in‐depth understanding of GDY and promote the advancement in the development of next-generation photocatalytic systems derived from carbon materials.