Mr Yearsley will be responsible for the new direct-to-client investment service Charles Stanley Direct which the company hopes to launch early next year.
He previously worked at Hargreaves Lansdown for 14 years as an investment manager with experience in open-ended funds and venture capital trusts.
Within his new role, Mr Yearsley will be responsible for driving the investment research offering and establishing Charles Stanley Direct in the direct-to-client investment market.

Mike Lilwall, group PLC director of Charles Stanley, said: "We are delighted that Ben has chosen to join the Charles Stanley Direct team ahead of the launch.
"Ben's appointment will be key in terms of communicating Charles Stanley Direct's industry-changing messages, pricing structures and client service offering and I look forward to his contribution to the team over the coming years."
Mr Yearsley said: "I am looking forward to being a part of Charles Stanley Direct and working with both the existing team and the wider Charles Stanley Group. I am very confident that the direct proposition that Charles Stanley has been developing will not be just another transaction platform and I am excited to be joining the team at this stage of its development."