Chief executive Peter Elliot-Hughes said DMA would provide the ideal platform for the company's dispute resolution and multimedia services.
He added that the deal would help NBA Quantum to target the US domestic market. He said: "It's a big step for us – but it's a well-established company and we plan to open another two offices." DMS' clients include private and public organisations that are involved in new-build and renovation projects.
Neil Sinclair, who set up DMS in 1985 and is the sole shareholder and chief executive, will continue to run it, and will join NBA Quantum's main board.