The new contractor will employ 3,500 people across the UK and will be led by Ian Sutcliffe, chief executive of Keepmoat.
Keepmoat is presently in consultations with hundreds of staff about planned redundancies at the merged business after a management shakeup at the top.
The boards unveiled plans to merge last July and said that Apollo will help to strengthen Keepmoat’s maintenance capabilities in the north and Keepmoat would boost Apollo’s new build capabilities in the south.
Ian Sutcliffe, chief executive of the merged companies, said: “I am very pleased to announce the formal completion of the merger between Keepmoat and Apollo.
There is compelling rationale for our coming together as we have joined two strong businesses with the vision of becoming the leading player in our sector with national coverage and a comprehensive client offering.
“We have already made substantial progress in terms of integration and, whilst there is still plenty of work to be done, I am confident that we are now well-placed to successfully deliver on our business objectives and I therefore look to the future with great optimism.”