•A novel precast ultra-lightweight ECC-concrete composite slab is investigated.•The four-point bending tests were conducted on six full-scale composite slabs.•The proposed slabs exhibited excellent flexural behavior and cracking resistance.•The specific bearing capacity of slabs was increased significantly by using ULECC. Precast concrete (PC) slab has extensive application in PC structure. The conventional PC slab is susceptible to cracking during transportation and hoisting, due to the low tensile performance of normal concrete. Besides, the large self-weight of normal concrete also impedes efficient PC slab construction. Unlike normal concrete, ultra-lightweight engineered cementitious composite (ULECC) with a combination of low density and high tensile performance is a promising material for PC slab construction. The objective of this research is to investigate the feasibility of using ULECC in novel PC composite slab to reduce its self-weight, while improve the flexural performance. The effects of precast ULECC thickness, lattice girders configuration, and overall slab thickness on the structural performance of ULECC composite slab were investigated. The introduction of ULECC for the precast plank improved load bearing capacity by 29% with the self-weight decreased by 24% than the control specimen. Multiple micro-cracks appeared in tensile zone due to high tensile performance with excellent crack width control capacity of ULECC. The structural performance of PC slab is further simulated by ABAQUS and demonstrates good consistent with the experimental results. This research lays the groundwork for the application of ULECC in PC slab for an efficient construction and high flexural performance.