Ronaldo will face United at Old Trafford for the first time since leaving the club for a world-record fee of £80m in 2009 with the Champions League last-16 tie finely poised at 1-1.
The 28-year-old spent six successful years at United, and Mourinho believes that the reception he will receive from the home fans is more than deserved.
"I think he is fine as far as I am aware," said the Portuguese manager.
"I think any accolade he gets is more than deserved and I think the reception he will get from the crowd will be deserved.
"I am aware how well he did here and what an impact he had at the club."
Ronaldo scored 118 goals in 292 games for United, winning three Premier League titles, a Champions League, an FA Cup and two League Cups in the process.