The use of braces equipped with shape memory alloys (SMAs), owing to their self-centering capability and ability to reduce residual deformations, can improve the seismic performance of steel frames. However, neglecting soil–structure interaction (SSI) may lead to inaccurate estimates of capacity, fragility, collapse safety, and resilience. This study evaluates the effects of nonlinear SSI on 3-, 6-, and 9-story SMA-braced steel frames modeled under fixed-base and SSI conditions. The frames were subjected to incremental dynamic analysis using 44 far-field ground-motion components. Fragility curves were developed based on HAZUS damage states, and collapse performance was assessed using the adjusted collapse margin ratio. The results show that SSI generally reduces seismic capacity and increases vulnerability, although its effect depends on frame height. The adjusted collapse margin ratio decreased by about 30% and 24% for the 3- and 9-story frames, respectively, while it increased by about 13% for the 6-story frame. The 9-story frame did not satisfy the FEMA P695 acceptance criterion, mainly due to fracture of SMA segments. At the MCE level, SSI reduced the resilience index of the 9-story frame by about 10.5% and increased the recovery time to 438 days. Therefore, controlling the strain demand of shape memory alloy components and considering soil–foundation conditions are essential for safety and resilience assessment.