This article addresses the multiple effects of nano-silica and hybrid fibres on the properties of an Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) incorporating waste bottom ash (WBA). The design of the concrete mixtures was based on the aim to achieve a densely compacted matrix, employing the modified Andreasen and Andersen particle packing model. The workability, porosity, flexural and compressive strengths of the UHPFRC are measured and analysed. The results show that due to the existence of the metallic aluminium particles in WBA, the generated hydrogen can cause some visible macro-cracks in the concrete, which could reduce the mechanical properties of the concrete. However, with a simultaneous utilization of nano-silica and hybrid fibres (steel and polypropylene fibres), the negative influence from the WBA can be effectively minimized and the flexural strength of the UHPFRC can be improved.