Although the size of ESG investment has increased significantly around the world, the effectiveness of ESG as an investment strategyis inconclusive and mixed. In this regard, this dissertation examines the performance of well-known ESG investment strategies (positive and negative screening) and suggests ways to strengthen them. By testing theCarhart(1997) four-factor model, this study confirms the ESG Integration, which combines style investment based on stock market anomalies and common ESG investment strategies, creates performance improvement in the long-term, resulting in higher excess return than existing ESG strategies. In particular, when strategies such as Size and Momentum are combined with ESG, there is a great improvement in performance. This study also confirms that combining style strategies with ESG can lower the risk compared to traditional style strategies (style only). The results of this study are meaningful in that it paves a way for investors to achieve the purpose of ESG while strengthening their investment portfolio.