Geopolymers represent an innovative eco-friendly repair material due to exceptional mechanical properties and durability under high temperatures as well as in acidic and marine environments. This study applied molecular dynamics simulations to investigate the bonding mechanisms, interfacial interactions, and failure processes at the interfacial transition zone (ITZ) between geopolymer mortar and ordinary Portland cement concrete (OPC) under varying temperatures and moisture conditions. Results indicate that moderate temperature increases enhance interfacial interactions and bonding strength, whereas excessive heat compromises chemical bond stability, leading to reduced strength. Fracture behavior across different temperatures is characterized by three distinct stages, each demonstrating notable fracture toughness. Additionally, moisture presence at the interface alters interaction dynamics, reducing both bonding strength and ductility.