This study investigates the hybrid joining of cast aluminum AlSi10Mg and DP600 steel using refill friction stir spot welding (refill FSSW) integrated with adhesive application. Box Behnken Design (BBD) was employed for experimental design, enabling a detailed statistical investigation of the effects of process parameters on joint strength and macrostructure. The final correlations for predicting joint strength in both non-adhesive and adhesive-assisted configurations were obtained through regression analysis. Pre-clamping techniques, including clamping ring and full tool pre-clamp methods, were employed to improve adhesive squeezing. The results demonstrate that adhesive-assisted joints achieve significantly higher lap-shear strength, exceeding twice the strength of joints without adhesive. The findings contribute to advancing refill FSSW for multi-material applications, particularly in automotive structures.