Over the past two decades, exchange traded Funds (ETFs) have emerged as a prominent investment vehicle for both institutional and retail investors, owing to their intraday liquidity, cost-effectiveness, and capacity to track market indices. This thesis examines the unintended consequences of the growing influence of ETFs on the stocks they hold, focusing on three key areas: volatility, liquidity, and price efficiency. Through a detailed analysis of U.S. and international stock markets, this study finds mixed evidence regarding the impact of ETF ownership on stock volatility. In the U.S., there is a modest increase in volatility following ETF ownership, while international stocks show no significant correlation. The research also highlights a decrease in liquidity and price efficiency associated with ETF growth in both markets, pointing to potential risks in liquidity management and price formation mechanisms. These findings contribute to ongoing discussions on the broader implications of the rise of passive investing through ETFs.