Self-compacting concrete (SCC) has been increasingly applied in complex reinforced concrete structures due to its high flowability and ability to achieve proper compaction without mechanical vibration. However, the structural behavior of SCC flat slabs with openings, particularly in the vicinity of columns where stress concentrations occur, requires further investigation. This study aims to evaluate the structural performance and failure behavior of SCC flat slabs with various opening configurations under monotonic loading. A nonlinear finite element analysis was developed and validated against experimental flat-slab results to investigate load–deflection behavior, stress distribution, stiffness degradation, ductility, and energy dissipation capacity. The numerical model showed good agreement with experimental results, with maximum deflection differences of 1.129%, 6.081%, and 9.555% for NC-1, NC-3, and NC-4 specimens, respectively, confirming the reliability of the developed model. The results indicated that the opening configuration significantly influences the structural response of flat slabs due to changes in load-transfer mechanisms and stress distribution around the column regions. Fewer openings, smaller opening dimensions, and openings positioned along the longer side of the column resulted in improved shear resistance and structural performance. The novelty of this study lies in providing a validated numerical assessment of SCC flat slabs considering different opening configurations and their influence on strength, deformation behavior, and failure mechanisms.