After pursuing a master's degree in economics, Herro took a job starting and managing an international stock fund with
Principal Financial Group. After, three plus years at The Principal Group, Herro took a similar position at The State of Wisconsin Investment Board. In 1992 Herro joined
Harris Associates. In 1994, Herro was described as the leader of a group of shareholders who worked to remove Maurice Saatchi, The Chairman of the company, from his position on the Saatchi Board of Directors. In 2006 and in 2016 Herro was named International Fund Manager of the Year by Morningstar and in 2010,
Morningstar named Herro the International Stock Fund Manager of the Decade. Herro founded and serves as co-manager of Oakmark International Fund, The Oakmark International Small Cap Fund and The Oakmark Global Select Fund, all advised by Harris Associates. ==Political activities==