"Playing a droll alien is something of a stunt role, the equivalent of a fat pitch down the middle for someone as talented as Spacey," writes Kenneth Turan in the Los Angeles Times, "and the satisfying thing about "K-PAX" is not that the actor is good at it, but how he goes about making the role his own."
Jay Carr in the Boston Globe simply marvels at Spacey's work in the film: "It is a beautifully modulated performance," he writes, "with a wide and subtle range of colors and feelings, and a delicious helping of deadpan humor just for dessert."
By and large, the movie is receiving lukewarm reviews, the best of them from Rita Kempley in the Washington Post: "Primarily, it's a warm, fuzzy and funny duet between Spacey and Bridges, one that brings to mind the interplay between Spock and Kirk. The picture never quite reaches the stars, but it definitely rises above much of what passes for entertainment today."
However, Carrie Rickey concludes in the Philadelphia Inquirer: "K-PAX is much better served by its actors than by its screenwriters."