Kiln's results soared by 270% in the first six months to a technical profit of £8.1m from £2.2m in the same period last year.
The Lloyd's operator's profit before tax increased to £3.5m, up from £1.2m tlast year.
Strong trading conditions helped the group bring its combined ratio down to 95% from 103% at the same point last year.
Despite the company's progress, it will not pay an interim dividend and chief executive Edward Creasy said Kiln wanted to make the most of the current hard market.
Kiln has shifted away from equities, but still chalked up a £2.2m loss on investments.