Ultra-high-performance concrete (UHPC) is an advances and novel cementitious composite with superior structural strength and durability properties. A blend of lower water-binder ratio, pozzolanic materials, fillers, and chemical admixtures results in a denser mix, leading to enhanced mechanical and durability properties. The fibre aspect ratio significantly impacts both the mechanical and damage characteristics of Ultra-high performance fibre reinforced concrete (UHPFRC). This research focuses on investigating the impact of fibre aspect ratio on the mechanical and fracture behavior of UHPFRC. Flexural strength tests were conducted on prism specimens (500mm×100mm×100 mm) with two different fibre aspect ratios 37.5 and 65. Fracture properties of UHPFRC composites were evaluated using specimens (700mm × 150mm × 80 mm). the nondestructive acoustic emission (AE) technique was utilized to capture fracture characteristics ahead of the crack tip in the presence of different aspect ratio fibre. The results infer that with an increase in aspect ratio from 37.5 to 65, both flexure and fracture strength are superior. Furthermore, the aspect ratio is significantly influencing the post-cracking phase more than that of pre-cracking.