Brooks Macdonald International saw its funds under management rise by 2.8% over the last six months to reach £2.58bn.
Organic net new business was also up 0.5% in the latest quarter, alongside strong investment performance, the firm said.
Meanwhile, group net flows were up 55% compared to the previous quarter.
Chief executive Richard Hughes said: "This has been a strong half year for Brooks Macdonald International, reflective of the momentum we see across the Group.
"It is pleasing to see a return to positive net flows for us as well as a rise in our [funds under management] to reach a new record level, in a period which was made particularly significant by the launch of our new Isle of Man office as part of our future growth strategy."