Mencap Pension Plan, London, hired Kempen Capital Management as fiduciary manager, said a spokeswoman for the charity.
She added the pension fund had worked with another provider previously, but she did not identify the firm.
The pension fund of the Royal Mencap Society has £120 million ($161 million) in assets.
The trustees launched a search at the end of last year, said a news release by Kempen.
Kempen has full discretion with respect to both asset allocation and manager selection.