Mbappe, who has scored 30 goals in 29 games this season, was an unused substitute in Saturday's 3-1 win over Lille, a precaution taken after he took a knock to his ankle three days previously in another 3-1 win, over Brest in the Coup de France.
The French forward has played the full 90 minutes in all six Champions League games this season for PSG and that doesn't look like changing when they host the Spanish side in Wednesday's first leg.
"When a team has a player like Kylian Mbappe, of course, we know that the more he plays the better because we all benefit from that," Luis Enrique told a press conference.
"There is no doubt about it. He could have played (on Saturday) if it had been a final, but it wasn't, it was not worth the risk. Kylian Mbappe is available, just like the other players."
The manager could afford to rest Mbappe in the league, where PSG now have an 11-point advantage at the top over Nice, and have gone 16 games unbeaten, but in the Champions League it hasn't all been plain sailing.
PSG finished second in their group behind Borussia Dortmund and lost to Newcastle United and AC Milan. They are also without a win in their last three games in the competition, a sharp contrast to Real Sociedad.
Real may be struggling domestically, seventh in LaLiga, but they topped their Champions League group, which included Inter Milan, and are undefeated in Europe this season.
"Real Sociedad have a tight defence in the Champions League, they don't give the ball away easily. We have to press them aggressively," Luis Enrique said.
"They are certainly one of the best teams in the competition, that is why they qualified as group winners. They were in a group with last year's finalists."
