Belgium international Hazard has not featured since Chelsea's 2-0 win over Paris Saint-Germain in the Champions League quarter-final second leg on April 8 due to a calf injury.
But the 23-year-old is now set to provide a welcome boost to Mourinho ahead of the semi-final second leg with Atletico at Stamford Bridge, with tie delicately poised at 0-0.
"He's ready, it's my option to start him or not to start him but he's ready," Mourinho said.
While Hazard is available, Mourinho confirmed goalkeeper Petr Cech will miss out, despite suggestions the Czech may start after he trained earlier on Tuesday.
Mourinho added: "Everybody is ready and wants to play, but obviously his condition does not allow him to play. But the message from him and the group is that they want to play, but of course his condition doesn't give him a chance."
Chelsea may head into the encounter with home advantage, but Mourinho believes the fact Atletico can progress with a score draw is a huge bonus for the Liga leaders.
"We play at home but a draw with goals is good for them and no good for us," he continued. "So you can't say who has the advantage. 0-0 is 0-0, to play at home is to play home, but to have the advantage of a draw with goals is good for them.
"Everything is balanced. We have to enjoy it, the players are the same. Every match is a match but some are special matches. Everyone wants to play the Champions League final, but before that is the semi-final of the Champions League."
The Portuguese was also questioned on his tactics, after a backs-against-the-wall performance saw Chelsea defeat Premier League title rivals Liverpool 2-0 at Anfield on Sunday.
That led to Liverpool manager Brendan Rodgers accusing his counterpart of "parking two buses", yet Mourinho said the Northern Irishman had since been in contact to congratulate him.
"Brendan is a manager and is somebody I consider my friend," Mourinho added. "I met him a long time ago when he was a very young coach, coaching kids (at Chelsea).
"I consider him a friend. Of course I know his words after the match, I also know his words today and today he told me congratulations for a great victory and a great performance.
"Especially because he is somebody I consider a friend and (somebody) I like, I prefer to forget the words after the match and I keep the words today.
"He's an intelligent guy, he will have watched the match on video and now he understands what happened."
