<p>Wire arc additive manufacturing (WAAM) has emerged as a cost-effective directed energy deposition technique for fabricating and repairing large metallic components. However, controlling bead geometry remains a critical challenge affecting dimensional accuracy and process reliability. This study systematically investigates the influence of key WAAM process parameters on bead geometry in low-carbon structural steel, establishing predictive and optimization frameworks applicable from single-bead to multi-layer wall fabrication. A central composite design is employed to vary wire feed rate, torch travel speed, torch tip distance, and gas flow rate. Second-order regression models are developed for bead height and width, demonstrating excellent predictive accuracy (<i>R</i>² &gt; 0.99, predicted <i>R</i>² &gt; 0.95) with prediction errors below 6.5%. Multi-objective optimization using desirability functions is performed to achieve target bead dimensions, and optimized conditions are applied to fabricate a multi-layer wall. Results show that wire feed rate and torch travel speed dominate bead geometry, while torch tip distance and gas flow rate have interactive but secondary effects. Microstructural analysis reveals a ferrite-based multiphase structure, characterized by hardness gradients peaking at an average of 186 HV₅ in the top layers, and tensile properties with an ultimate tensile strength of 496&#xa0;MPa, yield strength of 377&#xa0;MPa, and elongation exceeding 47%, comparable or superior to those of wrought low-carbon steel. This study demonstrates that robust empirical modeling and optimization enable accurate prediction and control of bead geometry, providing a reliable framework for producing dimensionally precise and mechanically sound WAAM-fabricated steel components.</p>