McLeod, who joined what was Shandwick in 1997, leaves the firm later this month. He will announce his next move in the coming weeks.
EMEA CEO Tim Sutton said in an internal announcement: "It is with great sadness, but also considerable gratitude, that I have to announce that Jon McLeod is to leave Weber Shandwick.
"Jon approached me earlier in the year to say that he was looking for another challenge. Of course, I respected that decision and wish him every possible success in his new ventures."
A head of the Manchester office was confirmed in February last year, while a deal was struck later in 2017 to create an alliance with financial PR specialist Tavistock, while director Nick Oborne remains the most senior financial specialist within Weber UK itself.
Sutton said that alongside recently departed EMEA CEO Colin Byrne, McLeod was "the person who has done most to define WS's UK corporate and political offer over very many years and should feel very proud of his contribution to the company".
McLeod said: "I am grateful to Tim and the impressive range of colleagues and clients that I have worked with over the past 21 years."