In the six months to 31 July, revenues rose 16% to £93.5mln while adjusted pre-tax profits rose by 13% to £12mln, boosted by acquisitions and client wins.
In July, the group bought B2B content marketing agency Velocity and B2B market research consultancy Circle.
In September, the company purchased Elvis, an integrated digital agency, and market research specialist, Charterhouse Research Limited.
Other acquisitions include the Publitek, Pinnacle and Twogether agencies, which Next 15 said are high margin and high growth businesses.
It also acquired London-based market research agency, HPI, which has been merged with Morar to create MIG Global.
“The group has continued to invest in agile companies operating in this augmented value chain and in the first half, group revenue grew by 16%,” said chairman Richard Eyre in a statement.
“The addition of several businesses to the group has been matched by some important client wins including LG Electronics, GrubHub, Marvell and NTT Data.”
In the first half, client wins included the likes of electronics giant LG and online food ordering platform GrubHub.
On the back of its expansion, the strong performance in the first half is expected to roll over into the second half with Next 15 saying it has been “encouraged” by trading so far.
In August and the first few weeks of September, it saw “high single digit” organic revenue growth.
“The prospects for the second half remain good. As a result, the board remains optimistic about the outlook for the group and is confident that it will meet its expectations for the full year.”
The group raised its interim dividend per share by 20% to 1.8p.
Strong full year
The first half followed an equally robust full year.
For the year ended 31 August 2016, Charterhouse reported turnover of £2.69mln, adjusted profit before tax of £0.59mln and net assets of £0.78mln.
“Next 15 is committed to building a deep data and insight capability at its core. Charterhouse is an important step in that strategy, significantly enhancing our financial services offering,” said Next 15 chief executive Tim Dyson.
“The combination of MIG’s technology driven consultancy and data offering with Charterhouse, a leading specialist in financial market research, will help drive deeper and more actionable insights to the financial services industry.”