Hargreaves Lansdown added 30,000 new clients and £1.54bn in new business during the three months to 30 September.
The firm said the increase in new business was "driven by improved market sentiment, continued investment in our digital marketing presence, an increase in client numbers and their continued wealth consolidation onto our platform".
"We also benefited from significant transfer activity relating to operational issues on a competitor platform, showing the benefit of our strong reputation for client service," said Hargreaves Lansdown.
The investment group reported assets under administration (AUA) stood at £82bn on 30 September, an increase of four per cent since 30 June.
The company also reported net revenue of £104.1m in the year to date, up 15 per cent on the £90.5m reported this time last year.
"I'm pleased to report a solid start to the new financial year for net new business and revenue," said Chris Hill, chief executive.
"We continue to place clients at the centre of what we do and our relentless focus on the level of service that we provide is enabling both existing and new clients to save and invest with confidence."
In August, the group reported a 21 per cent rise in annual profits, while total AUA jumped by 28 per cent.
Hargreaves Lansdown benefited from last year's Brexit vote, with a 51 per cent hike in equity deals in the wake of the referendum.
Shares in the group dipped 1.9 per cent in early trading.