The contract has been on the table all summer, but the Belgium international held back from putting pen to paper until he was confirmed as the Blues' No. 1.
Mourinho's team selection for the 3-1 win over Burnley on Monday night demonstrated his faith in the 22-year-old and he is now set to sign an extension that runs until 2019.
Courtois has two years remaining on his current 37,000-euro-a-week contract and the new package will bring him in line with the second tier of earners at Stamford Bridge alongside the likes of Ramires, Gary Cahill and Branislav Ivanovic.
Real Madrid, Paris Saint-Germain and Monaco are closely monitoring Cech’s situation and formal bids could now be forthcoming following confirmation of the 32-year-old’s downgraded status.
Mourinho said Monday that he wants to keep Cech but the West Londoners are believed to be ready to cash in on the keeper, who has two years remaining on his current contract, if they receive an offer of 12 million euros.
Chelsea already has an experienced understudy in place should he leave. Mark Schwarzer, Cech’s backup last season, signed a one-year extension in July.