The trust's board has announced Troy will replace Martin Currie as its investment manager in a move it hopes will "steadily grow" its portfolio's income.
Troy is expected to take up the position in October, alongside PATAC Ltd as the alternative investment fund manager.
The announcement follows a review of the trust's management arrangements, which the board kicked off in June when the trust's previous manager, Mark Whitehead, resigned from Martin Currie.
Securities Trust of Scotland told the market Troy would make a "significant contribution" to costs by waiving its management fee for 12 months.
The trust said its new investment manager would also make a "significant ongoing annual contribution" to the cost of the company secretarial and administration services to be provided by PATAC.
John Evans, chairman of Securities Trust of Scotland, said: "The board's objective throughout the recent search process was to find a team with the resources, record and skills to continue to achieve the company's objectives.
"We believe that in PATAC and Troy we have an excellent outcome and we look forward to a long and successful working relationship with all of them."
The trust's portfolio will be managed by James Harries, supported by Tomasz Boniek. There will be no change to the trust's investment objective.
Mr Harries already manages the Troy Global Income fund, which is in the 10 top performing funds over the past three years in the IA Global Equity Income sector.
The Securities Trust of Scotland has returned 24 per cent over the past three years while its sector, the AIC Global Equity Income, has returned 11.5 per cent.