AUM hit £8.2bn by 31 December 2017, up from £7.3bn on 1 October 2017.
The firm has £7.7bn in listed equity funds, £454m in private equity funds and £22m in property funds.
Ian Simm, chief executive of Impax, said: “I am pleased to report on another outstanding quarter. Investor interest in the transition to a more sustainable economy continues to gather momentum and it is most encouraging to see further strong inflows across our fund range from clients in Europe and North America.
“Our pipeline remains promising for both our listed and private equity strategies.”
The firm said the figure does not include assets managed by Pax World Management, a company Impax announced it would acquire last year. The deal is yet to be completed.
