Philip Pearson and Anthony Burton want to pursue other opportunities. The assets will be rolled into other funds.
The pair will stay on to manage the £193m fund and its transition until the end of 2015 before leaving the company.
Pearson has been with the company since 2001, while Burton joined in 2008. The duo have been managing the fund together since 2009.
Over the past three years the fund has returned 10.63%, while over five years the figure is 10.73%, according to Morningstar.
Man GLG declined to comment.