Germain Lussier reviewed Knock Knock for SlashFilm and gave it a 7/10. Here are some quotes:
For almost half of Knock Knock, the film presents fresh, difficult and exceedingly awkward situations for the characters. And because you have no idea what’s going to happen, that’s scary and thrilling in its own unique way.
We aren’t used to seeing him as a dad and it feels off. But once the family leaves and he’s on his own? That’s a role he’s perfect for and when Knock Knock really gets cooking.
…Knock Knock is another strong example of Eli Roth doing what he does best: Building tension, asking questions, and making the audience uncomfortable. A few bumps aside, Knock Knock is an enjoyable, original ride.
Eric Kohn reviewed the film for the Indiewire and gave it a C. Here are a few quotes:
“Knock Knock” at least provides an enjoyably ridiculous Keanu Reeves performance and some clever stabs at satirizing white collar America. The movie’s uneven tone and ridiculous twists never quite gel, but “Knock, Knock” is so eager to please that it’s hard not roll with the absurd depravity on display
Offering little in the way of depth, “Knock Knock” never lands the scary-funny tone of Roth’s earlier movies; instead, it drowns in cheap thrills.