Hershey has handed president and CEO J.P. Bilbrey the role of chairman.
The US confectioner will take on the third job immediately, replacing Jim Nevels, who becomes lead independent director at the Reese's owner.
Hershey said Nevels had suggested giving Bilbrey the position "to underscore its confidence in Hershey, the existing management team and Bilbrey".
Nevels said: "These changes to our Board are the result of careful thought and consideration by the full Board and are consistent with our vision for continuing to deliver sustainable growth and build on the legacy of our great company J.P. is one of the most effective leaders in corporate America. Throughout his career, industry groups, government and corporations have turned to him for his thoughts and perspective on the changing dynamics of global food trends. We are fortunate that J.P. will continue to lead the company in this added capacity and I, as well as my fellow directors, look forward to working with J.P. as we continue to build value for all shareholders."
Hershey said Nevels would have "expanded duties and responsibilities" as lead independent director, including liaising between Bilbrey and the independent directors, approving board meeting agendas and schedules, and assisting with succession planning and crisis management.
Bilbrey became Hershey's president and CEO in 2011. He was promoted from COO.