The 34-year-old, who on Saturday scored for a second straight game in the 2-0 Boxing Day defeat of West Ham, is out of contract in June, but remains a mainstay of Mourinho’s Barclays Premier League leaders.
“It’s a formality,” the Portuguese boss said.
“There are no doubts that he is going to get another contract. I know that, he knows that.
“We in the club, in the board, we know that and I think also you have to feel that. Without us confirming anything, you have to feel that.
“He’s a very important player in the team so the next contract sooner or later will come.”
Chelsea have a policy of offering those over 30 only one-year deals, irrespective of their status.
Terry is bidding to lead Chelsea to a fourth Premier League title and a first since 2010.
The Blues play at Southampton on Sunday aiming to finish 2014 on top of a table which includes a number of teams who could yet topple them, according to Mourinho.
“I have lots of experiences of coming from behind or being top of the league; I prefer to be top of the league and the players are exactly in the same line as me,” Mourinho added.
“It is better to be in front. We play and we think about ourselves.
“Below 15 points (gap to Chelsea) you are in the title race. More than 15 points, it is an impossible job.”
Chelsea have 45 points, with Manchester City second, three points behind, and Manchester United 10 points adrift in third.
Southampton are fourth, West Ham fifth, Arsenal and Tottenham sixth and seventh, with 30 points each.
Mourinho joked with Hammers boss Sam Allardyce prior to Friday’s win, which was convincing.
“I asked Big Sam before the game, I said: ‘What do you want, win the title or finish in the top four?’
“He said, ‘I want to be one position after Chelsea’.
“It’s difficult but you have to say it is realistic. They are getting results, they are playing well. Why not?”
Southampton, with boss Ronald Koeman required to overhaul the squad left behind by Mauricio Pochettino, are in a similar position to the Hammers, according to Mourinho.
“Any one of them who finishes top four, it’s a super achievement,” Mourinho added.
“If he does that, it will be an amazing achievement for them.”
Few teams boast players of the talent of Eden Hazard, who will be key if Chelsea are to win Mourinho’s third Premier League crown.
The Belgium playmaker is yet to win the championship at Chelsea, where his sole trophy is the 2013 Europa League from his first season at Stamford Bridge.
“He’s a happy guy on the pitch. He doesn’t feel the pressure, he doesn’t feel responsibility, he just wants to enjoy it,” Mourinho said.
“He plays in the first minute like he plays in minute 90. It doesn’t matter the result – fantastic, no pressure – and that’s a good feeling for me.”
Mourinho has encouraged Hazard to combine hard work with his dazzling trickery.
“He didn’t lose his spontaneity, he didn’t lose his happiness, he didn’t lose his creativity, none of his good qualities, but he won some other qualities,” Mourinho said.
“Even physically, look at him – he’s a small guy but he’s very strong.
“He scores with his head, jumps well, he’s strong to hold off contact from opponents.
“We are doing that progressively. We didn’t try to do that by flicking a switch. It’s progressive and a great evolution.”