Andrew Howie, managing partner of Grant Thornton's Scottish practice, said the accountancy firm benefited from hiring more senior staff in specialist areas like tax in the six months to December.
After sanctioning appointments that will add £2 million to the firm's annual paybill, Mr Howie said the recruits have helped Grant Thornton expand in areas of the market that are growing.
He also said first half revenues were up on last year.
He said: "The early signs are encouraging that the investment will pay off.
"If you just do what you've always done it's not going to work."
The firm has been providing advice to clients on how to make the most of tax breaks on investment after hiring Bryan Crawford as a director specialising in Capital Allowances, from Ledi Consulting.
Mr Howie noted Grant Thornton acts for a number of Scotch whisky firms.
Tax director Vishal Chopra and Sandra Rodger, a partner in assurance, joined from PriceWaterhouseCoopers.
Mr Howie said Grant Thornton's Scottish arm performed in line with the UK business in the year to June. Grant Thornton grew UK revenues 10.6% annually, to £417m. The company did not disclose a figure for Scotland.
Mr Howie said profits were flat in Scotland in the year to June, reflecting the investments it had made.
A Grant Thornton in Scotland spokesman said it is planning a rise of just over 10% in revenues this year.
Mr Howie said the firm has taken on 41 new people in the last 12 months in Scotland. It expects staff numbers to increase by 5% in the current financial year, after taking account of leavers. Grant Thornton employs around 180 people in Edinburgh and Glasgow.