The objectives of this study were to 1) examine the impact of strategic management accounting (SMA) that influences business sustainability by integrating comprehensive internal information and external business environment to formulate strategic decision-making to enhance competitiveness, and 2) investigate the serial mediating role of business strategies and competitive advantages. Data were collected from a total of 168 samples of listed companies in the Stock Exchange of Thailand and analyzed by using partial least squares structural equation model. The results showed that strategic management accounting had a positive direct impact on innovation-oriented strategy, efficiency-oriented strategy, and sustainable performance. Innovation-oriented strategy and competitiveness was found to have serial mediating effect on strategic management accounting and performance sustainability. However, both efficiency-oriented strategy and competitiveness had no serial mediating effect on strategic management accounting and sustainable performance. The implications in this present study confirm that strategic management accounting plays a significant role in determining effective business strategies; therefore, executives need to focus on related resources to foster the strategic management accounting which in turn enhances the firm’s competitiveness and sustainable performance.