BlackRock will replace Newton Investment Management as manager of Quilter Investors' UK Equity Growth fund.
BlackRock's Nick Little, currently manager of the BlackRock UK fund, will take over management responsibilities from the Quilter portfolio, the firm said on Tuesday.
Quilter said BlackRock had been chosen to replace Newton, which had run the fund since 2017, due to its "experienced team and disciplined investment process within the UK growth space".
CEO and head of investments at Quilter Investors Paul Simpson said: "BlackRock has been a global partner for a number of years now, so we know they can produce sustainable growth over the long term for our clients and investors.
"We are delighted to welcome Nick Little to our UK Equity Growth mandate and are excited to see where he takes the portfolio.
"These partnerships allow us to give our investors a range of insight and expert portfolio management, and we look forward to working closely with the BlackRock team on this mandate."
Little said it was "an honour" to take on the portfolio, adding: "There is a lot of economic and financial market uncertainty at the moment, which makes this is a great time to be finding and investing in differentiated companies that can still deliver sustainable growth and returns."
The fund targets between 35 and 55 FTSE 350-listed holdings, with some international exposure, Quilter said. The fund is used within Old Mutual Wealth's managed portfolio service, WealthSelect.
Under Newton's management, the fund returned 1.4% in three years, ahead of its FTSE All-Share benchmark's loss of 2.5% and its Investment Association UK All Companies sector peers' reverse of 4.2%, data from FE fundinfo shows.
Since the fund's March 2013 inception date it is up 39%, compared to 34% and 37.5% from its benchmark and peers respectively.