In the last 20 years, institutional investors have suffered damage to their investments derived from corporate fraud, lack of transparency in the information given to investors, poor business management and defective decision-making processes. As a result of these losses, investment funds have recently changed the way in which they manage their portfolios. One response to the problem is activism, which requires getting into the inner workings of a target firm. As a result, the target firm adopts new decision-making processes which bring about change in business management to improve economic performance. This article basis itself on the theme of corporate government, and analyses activism and its impact on corporate government, and on business performance, taking the case of Mexico as its reference point.