Real landed the Togolese frontman on loan from Manchester City on Tuesday, presented him on Thursday and after only one training session with his colleagues opted to take him up to Pamplona for Sunday's clash.
"He's a player I like a lot, with a great deal of experience and he will do well here," the Portuguese told a news conference.
"He hasn't played since December, but he hasn't been injured and has trained every day. He is in a basic condition to play."
Adebayor has been brought in on a temporary basis due to the the back injury suffered by Gonzalo Higuain, though Real have the right to make the move permanent at the end of the season.
The arrival of the former Arsenal player puts the pressure on French striker Karim Benzema, who has been struggling to fulfil expectations in Higuain's absence.
Mourinho, who had been pushing for another centre forward since his arrival last May, gave little away as how he meant to deploy his new recruit.
"Having three strikers is the optimum situation for the team," he added.
"Benzema and Adebayor are different types of strikers but also complementary."
Second-placed Real trail leaders Barcelona by four points in La Liga, though that gap could grow to seven if the champions win at Hercules later on Saturday.