As chairman, 59-year-old Pettigrew will also sit on Miton’s board as a non-executive director.
He replaces Ian Dighe who stepped down as chairman earlier this year.
The news comes amid Miton’s latest results which reveal adjusted profits before tax fell 17.2% on the same period last year.
However, assets under management rose to £3.35bn as of 31 August.
Pettigrew said: “I am very excited to be joining Miton at this stage in its development. With its distinctive investment capabilities Miton has the opportunity to further develop its business model and deliver the best outcomes to its clients.”
The results also shed light on progress in the CF Miton Global Infrastructure Income Fund which has grown an AUM of £17.3m since launching in March 2017
David Barron, chief executive of Miton Group, said: “The group continues to deliver strong investment performance and net inflows. We have continued to streamline the business and have demonstrated the scalability of our operating platform.
“Following a strong start, we look forward to the full year results with confidence.”
