The client is not revealed, other than that it is one of the biggest banks in the world.
Styles & Wood said that the work would all be carried out in the UK and that there were three other contractors that had also been selected for this framework.
Mobilisation and induction has begun and project delivery is expected to start by November 2016.
Styles & Wood chief executive Tony Lenehan said: "We are delighted to have been selected as a delivery partner on this five-year framework, which provides further evidence of the strength of our business model, broadening customer base and diversification strategy. As new technologies and practices continue to drive fundamental changes within the banking and finance sector, our unique skill set, experience and technical capabilities leave us well positioned to provide the specialist services required by major financial institutions."