Investors pulled money from its funds as well as from GLG Partners, the rival hedge fund group it bought in October last year.
Yet Man still managed to grow its funds under management (FUM) to $68.6bn, boosted in part by the acquisition of GLG.
The company added $2.7bn on to the $25.4bn taken on from GLG and the $40.5bn it already held at the end of its second quarter.
Analysts say the loss of the $1.1bn investment would not impact on the future performance of the group, due to its relatively low basis point fee, and a suite of new products yet to be launched by the firm.
Shore Capital analyst Paul Dobbin said: “It gives the impression of another quarterly outflow, yet there are signs elsewhere of things improving. Without that [outflow] I think there would’ve been a different story.
“I don’t think anything changes in terms of the long-term story for Man Group.”
The company, which started as a sugar broker in 1783, said it held a regulatory capital surplus of around $300m and over $1.8bn in cash at the end of last year.
Chief executive Peter Clarke said: “With strong performance and a clear marketing focus for new and existing investment ideas, there is significant momentum for the business in the year ahead.”