Interest in Environmental, Social, and Governance (ESG) investing has increased substantially in recent years. Still, little research has been done into how ESG funds are being incorporated into portfolios by individual investor households. In this paper, the authors explore a unique dataset containing the demographic and portfolio characteristics of over five million households and identify those holding an ESG fund. Using an unsupervised machine learning technique called K-prototype clustering, the authors find five unique types of investors who have incorporated ESG mutual funds and/or ETFs into their portfolios. The authors then test to what extent incorporating ESG funds biases traditional portfolio construction decisions and find that ESG households have a strong growth tilt compared to similar non-ESG households. The research serves as a foundation for further study into the motivations behind, and portfolio implications of, implementing any of the identified ESG investment strategies.