MacAfee (pictured) joined Porter in 2000 as MD and rose to CEO in 2016 after Karen van Bergen was hired to lead Omnicom PR Group.
His departure follows news earlier this week that van Bergen is leaving her role to become dean of Omnicom University. The news also follows the departure in October of Porter Novelli global president Jennifer Swint - her former role was eliminated.
Van Bergen said: "I am deeply grateful to Brad MacAfee for his commitment and contributions to Porter Novelli over his nearly four years as CEO, and his 19 years with the agency. As we embark on this new chapter, we look forward to welcoming a new leader who can build on Porter Novelli’s incredible momentum as a global purpose consultancy in 2020 and beyond."
Under MacAfee's tenure as chief executive, which coincided with the agency's merger with sister shop Cone Communications in 2017, Porter has had a major focus on its global purpose practice.
Speaking to PRWeek early this year, MacAfee said: "Last year was big, pivotal and important for Porter. We have been shifting from a generalist PR firm into a global purpose comms consultancy."
In a statement announcing his departure, MacAfee said: "Working at Porter Novelli and serving as CEO for nearly four years has been a true honor and an adventure of a lifetime. The talent, culture and deep commitment to helping clients find, live and tell their purpose in order to make an impact on business and society is what makes this organization so special. Shepherding Porter Novelli through the acquisition of Cone Communications, establishing our Purpose practice and repositioning the organisation as a communications consultancy has been equal parts challenging and rewarding. Our position in the market is resonating and great things are in store for this organisation in 2020 and beyond."
In the UK, senior leadership changes in summer 2018 saw the promotion of Jo Patterson and Nicole Yost to deputy MDs and former MD Fenella Grey moving to a new chair role.
Porter Novelli generated estimated global revenue of $150.5m in 2018, a rise of one per cent on the prevous year, according to PRWeek Agency Business Report. It employed 720 people globally at the year end, including 65 in the UK, where its 2018 revenue was an estimated £9.7m.
This article was updated on Friday afternoon with comments from van Bergen and MacAfee.