This study investigates the mechanisms for optimizing the cost of capital in joint-stock companies operating under emerging market conditions, with a particular focus on the role of corporate financial structures in shaping capital efficiency and financial sustainability. The research develops a conceptual framework that integrates traditional capital structure theories with institutional and macroeconomic constraints specific to emerging economies. Using a mixed-methods approach, the study combines econometric modeling of firm-level financial data with comparative analysis across selected joint-stock companies to identify the determinants of weighted average cost of capital (WACC) and their impact on firm performance. The findings reveal that leverage ratios, ownership concentration, and access to long-term financing significantly influence capital cost dynamics, while regulatory stability and market depth moderate these relationships.