Abstract: In practical engineering, irregular structural layouts are common due to functional and architectural requirements. In steel-concrete composite frames, uplift-restricted and slip-permitted (URSP) connectors mitigate the tensile stresses in negative moment regions by releasing composite action, while engineered cementitious composites (ECC) offer excellent ductility and crack resistance. When combined in a composite frame, these technologies effectively reduce the risk of concrete cracking in negative moment zones. To study the applicability of URSP connectors and ECC in the seismic resistance of irregular steel-concrete structures, both plan and vertical irregular structures were designed to conduct modal analysis and elastic-plastic time-history analysis. Specifically, with a reasonable arrangement of URSP connectors, the influence of ECC layout range on the structure's natural vibration periods, displacement response, and plastic hinge distribution was investigated. The analysis results indicate that, due to the lower density of ECC compared to ordinary concrete, increasing its application in the irregular parts of the structure leads to a decrease in lower-order natural periods. Regarding seismic response, for the plan irregular structure, the effect of ECC differs between orthogonal and parallel directions relative to the protrusions: peak roof displacement and inter-story drift angle decrease as the ECC placement increases in the orthogonal direction, whereas they increase in the parallel direction. Therefore, a 1/5‐span ECC layout is recommended for the irregular regions of plan irregular structures. In the vertical irregular structure, the application of ECC tends to amplify the X-direction seismic responses.