This brings the total UK head count to 775, which is 325 more than Aedas AHR had when it started.
TCN marketing director Tony Williams said the merger would give the practice a national and international presence since Aedas was part of a global alliance with Australian and Asian practices.
Williams said: "It puts us in the frame for more exciting projects. There is no cash transaction; it is a natural merger."
Aedas, which now has seven UK offices, including London, Glasgow and Leeds, will gain a presence in the Birmingham and South-west markets.
It puts us in the frame for exciting projects. There is no cash transaction; it is a natural merger
Tony Williams, TCN marketing director
Aedas AHR chairman James Handley said: "We are already, between us, appointed on some of the biggest and most exciting projects in the Midlands, including the high-profile Masshouse scheme for Birmingham council."
Williams and TCN managing director Roger Ingall join the main board of Aedas.
The firm is an amalgamation of Abbey Holford Rowe with Peddle Thorp in Australia and LPT in Asia. It has a combined turnover of £30m. Before the latest merger it employed more than 800 staff working in six countries.
The board has five directors, including Handley and Peter Oborn from Aedas AHR.