Cech took part in training on the eve of the contest a week after being ruled out for the season by Mourinho with a dislocated shoulder sustained in the first leg.
The stopper departed after 20 minutes of last Tuesday's first leg after he punched the ball from underneath his own crossbar, with David Luiz pushing Raul Garcia into the Chelsea goalkeeper, who hit the ground with a thud and was replaced by Mark Schwarzer.
It was later revealed that he had dislocated his shoulder.
At the time, Jose Mourinho said: "Petr Cech's season over. Don't ask me technically, but season over.”
However, it appeared that the keeper may recover in time after taking part in training ahead of Wednesday’s match, but Mourinho insisted his number one trained alongside injured personnel, suspended players and those fully fit to show solidarity.
"Everybody's ready and he's ready and that's the message we wanted to give," the Portuguese said.
"Everybody was on the pitch.
"It's a very important match for our group. Everybody's together, everybody wants to help, everybody wants to play.
"His condition doesn't allow him to play, but the message from him and the group."
Terry limped off after turning his ankle in the second half of the 0-0 first-leg draw in Madrid and Mourinho said at the time that he was unlikely to play again this season.
Yet Terry, who missed Sunday's 2-0 Premier League win against Liverpool, trained on Tuesday and is fit.
"He is ready and he will start," Mourinho said at his pre-match news conference.
Eden Hazard, who went off after 17 minutes of their quarter-final, second leg against Paris St Germain, is also available, leaving Mourinho to decide whether or not he will start.
Goalkeeper Petr Cech, who dislocated his shoulder last week, is not fit, even though he trained yesterday.