The wealth manager issued a trading update for the for the first quarter of 2019, which revealed closing funds under management was £103.52bn.
At the same point the previous year the figure stood at £89.91bn.
The figures also revealed a slowdown in inflows, which were, according to the firm, a sign of “resilience” in the face of “economic uncertainty”.
Gross inflows slumped from £3.91bn in Q1 2018 to £3.61bn this year and net inflows fell from £2.60bn to £2.18bn.
Andrew Croft, chief executive, said: “We have experienced a good start to the year, attracting £3.61bn of gross inflows which, together with continued strong retention, has resulted in net inflows for the quarter of £2.18bn – equating to 2.3% of opening funds under management (9.1% on an annualised basis).
“This performance demonstrates the resilience of our business through the current political and macro-economic uncertainty.
“These net inflows, coupled with positive investment returns, have resulted in an 8.3% increase in funds under management to a record £103.5bn at the end of March.
“Whilst uncertainty will inevitably impact investor sentiment from time to time, it does not change the long-term needs of individuals.
“There remains both a growing market for trusted face-to-face advice in the UK and an advice gap that represents a major opportunity for us.”
He added: “Given the scale and quality of the St. James's Place Partnership we are confident of both the resilience of the business in more difficult times and our ability to continue to grow the business over the medium to long term.”