A nano-Al2O3 reinforced AgCu composite filler (named AgCuC) was developed by introducing nano-Al2O3 (2 wt%) into AgCu eutectic powder filler and then by high-energy ball milling. High-quality brazing of TC4 alloy to Al2O3 ceramic was achieved using the AgCuC filler. The typical interfacial microstructure of TC4/AgCuC/Al2O3 joint was TC4/α-Ti+Ti2Cu diffusion layer/Ti3Cu4 reaction layer/Ag(s,s)+Ti3Cu4+TiCu/Ti3Cu4 reaction layer/Ti3(Cu,Al)3O reaction layer/Al2O3. The addition of nano-Al2O3 in AgCuC filler could improve the interfacial microstructure by constraining the growth of continuous Ti-Cu intermetallic layers. Moreover, granular Ti-Cu phases reinforced Ag based composite is formed in brazed joint. Both the thickness of reaction layers and the size of granular Ti-Cu phases increase with an increasing brazing temperature, while the content of Ag based composite decreases. The highest shear strength of 67.8 MPa is achieved when brazed at 920 °C for 10 min. Typical fracture analyses show that the crack originates in the fillet, extends along the brazing seam and then transforms into Al2O3 ceramic, and finally fractures in the Al2O3 substrate side