The firm released the figures today in its interim management statement for the three months to 31 March 2012.
Operating income was up from £33.9m in 2011 to £37.9m.
Total funds under management were up six per cent from £15.8bn in December 2011 to £16.8bn.
This compared positively with the FTSE 100 which increased by 2.7 per cent over the same period.
The investment management division also saw acquired new business significantly rise from £42m in 2011 to £165m.
Some £82m of this new business related to the firm’s acquisition of London-based wealth management firm R M Walkden and Co earlier this year.
Investment management division figures are measured to 5 April to coincide with the key charging dates for private clients.
Mark Nicholls, chairman, said: “In spite of challenging investment conditions our first quarter’s net operating income was up 12 per cent on 2011. Total net growth in organic and acquired funds under management in our investment management business was £299m representing an annualised growth rate of over eight per cent.
“We are continuing to invest in people and systems to improve our service and efficiency and to respond to regulatory change. Whilst investment markets are expected to remain uncertain, Rathbones is as well placed as ever to develop future growth opportunities.”