This study investigates the bond behavior between Ultra-High-Performance Concrete (UHPC) and reinforcing steel subjected to elevated temperatures, with a focus on the influence of embedment length, concrete cover, and thermal exposure. Using the beam-end test method in accordance with Eurocode recommendations, a series of specimens were prepared with varying diameters (12 and 16 mm), embedment lengths (6d, 9d, and 12d (d: bar diameter)), concrete cover depths (1d and 2d), and exposed to three temperature conditions: room temperature (25°C), 300°C, and 600°C. The results demonstrated that temperature has a substantial effect on bond performance. While moderate heating (300°C) sometimes enhanced bond strength due to post-curing effects, exposure to 600°C caused significant bond degradation, characterized by reduced load capacity and increased slippage. Longer embedment lengths consistently improved bond strength across all temperatures, often shifting failure modes from pull-out to steel rupture. Increased concrete cover provided better confinement and thermal protection, though its influence was less dominant under severe thermal exposure. The findings contribute to a deeper understanding of the bond mechanisms in UHPC–steel systems and offer practical insights for the structural design of UHPC elements in thermally demanding environments, including fire-prone applications.