Mr McCann founded Patron Financial Advice nine years ago with David Hasib, and oversaw the merger of the firm with Infocus Wealth Management last year.
Mr McCann will remain as a director with Infocus, according to a statement from the firm.
Infocus managing director and chief executive Rod Bristow said: "During the merger negotiations, it was clear Rob was a passionate advocate of advisers and the advice industry."
"Our shared view of helping advisers operate better businesses in a changing world was a cornerstone for the success of the merger.
"Obviously it is sad Rob will no longer be involved in the day-to-day operations of the business," he said. "However, it's also very satisfying seeing him looking forward with excitement to the next part of his journey."
Mr Bristow added that Infocus will take the opportunity now to review its operational and adviser support teams.
"We continue to have one of the highest support staff to adviser ratios in the industry, reinforcing our commitment to helping advisers grow revenue, increase efficiency and effectively manage risk in their business," he said.
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