The Maidenhead-based firm said forward orders were up 10% to £3.2 billion in the first half of the year as it secured more than £700 million of new contracts and extensions in the period.
Costain said it was ramping up its dividend by a third, as adjusted pre-tax profit climbed 8% to £9.1 million. Revenues increased 14% to £529.1 million.
New contracts included an appointment to Network Rail's £2 billion electrification programme as well as work on a section of London's Crossrail project.
It also won a further commission with energy giant Centrica for its Barrow gas terminals project in Cumbria, as well as work for National Grid.
Chairman David Allvey said: "We have delivered a strong performance in the first half of the year."
He said a capital raise of £70.3 million this year had helped the group take advantage of opportunities "to accelerate the group's development", and that it remained on course to deliver a result for the year in line with the board's expectations.
Costain announced an interim dividend of 3.25p compared to 3.75p last year. It said that on the basis of the enlarged share capital it represented a 32% increase in the total pay-out to shareholders for the period.
The 150-year-old business has previously worked on a series of high-profile infrastructure projects in the UK including London's St Pancras station redevelopment and the Channel Tunnel rail link.
Current work includes a major nuclear decommissioning project at Sellafield and the redevelopment of London Bridge station for Network Rail.
Investec analyst Andrew Gibb said: "This is a good set of results, which underlines the rationale behind the recent capital raise."