Around 200 new jobs and 60 modern apprenticeships are set to be created as part of the contract, which covers the local authority's digital channel shift and aims to deliver efficiency and cost savings of around £45m.
CGI claims it not only aims to help the council via this partnership, but also intends on boosting the local economy in Edinburgh via job and apprenticeship creation and investing in social enterprises and community groups.
Although the contract will last for an initial term of five years, there is also the option to extend for a further five and other extension periods beyond that.
Citizens of Scotland's capital city will now be encouraged to carry out transactions online, while schools in the area will also benefit from the modernisation of their ICT infrastructure and an improvement of bandwidth which will allow both primary and secondary students better access to online learning resources.
The firm will also update the ICT resources at the local council itself and integrate back-office systems with a new Enterprise Resource Planning (ERP) system.
The ERP solution will integrate with customer-facing digital platforms in order to improve customer services whilst increasing efficiency and reducing costs.
"In signing this contract, we will transform the way we do business," claimed Councillor Alasdair Rankin, Convener of Edinburgh's Finance and Resources Committee.
"People are at the heart of our organisation, whether they are citizens, staff or working the in the city's economy.
"One of the exciting things CGI will do is to speed up our move to greater online capability giving residents and businesses greater flexibility to engage with the council and carry out their transactions digitally.
"This will make us a more efficient and effective organisation across our wide range of council services," he added.