The acquisition marks the Danish consultancy’s entry into the three sectors.
Cruz Atcheson offers concept design, due diligence support and project development in wave, tidal and floating wind.
All of its staff in Lisbon will join K2 Management following the acquisition.
With a presence in the Portuguese capital, K2 Management will now have 19 offices spanning six continents.
Its CEO Henrik Stamer said: "It adds another string to the bow of our already talented team. Bringing this expertise on board allows us to diversify out skillset across these burgeoning new technologies and benefit from the team’s extensive experience, enhancing our robust and specialist client services."
Neither party disclosed the value of the transaction.