D&D 5E Does "Nondetection" cancel out see invis?

[Ovinomancer]

Crawford says that is correct:

I run it like this for naturally invisible creatures, but not for creatures that are invisible through magic. At that point, the see invisible doesn't care about Bob the Nondetectable, but about the illusion around Bob the Nondetectable. It pierces the illusion, which isn't part of Bob. If Bob was a shapechanger, though, and in a different form, then nondetection would prevent True Seeing for seeing that, because that's now gathering information directly about Bob the Nondetectable.

But invisbility the illusion spell? Doesn't change anything about Bob, just cloaks him in an illusion, and that's still fair game.

 

[Wiseblood]

I had not considered it. Invisibility is commonly known. I only recall nondetection being used....never. Unless you count that amulet back in the 20th century.

 

[Mouseferatu]

I wouldn't have the players' adversaries use such a spell combination against them, that would hardly be sporting, but I wouldn't say no if my players decided to use this combination against their foes.

Not everything has to be sporting. Intelligent foes should behave intelligently.

IOW, would I have NPCs pull this trick often? No. But once in a while, especially if it's a main/recurring intelligent villain? Absolutely.