Arlo Wiley’s review published on Letterboxd:
Safety Not Guaranteed could so easily have fallen into the "quirky indie" trap, its premise involving a man who places a classified ad seeking a time travel partner. Luckily, the charm of its cast and the honesty of its screenplay ensure that it's more than just that. Filmmaker Mark Duplass, for once acting without directing or producing, is perfectly low-key as the possibly insane time traveler; and as a magazine intern investigating his story, Aubrey Plaza expands her typically deadpan persona to find a warm emotional core that matches his. Then there's Jake Johnson. I already liked him for his role as grumpy young/old man Nick on TV's New Girl, but here he shows just what a promising actor he is. His subplot, involving an attempt to hook up with an old classmate, often feels disconnected from the rest of the narrative, but he's so funny and compelling that he carries it. The narrative could use a little focus, though; I could watch a whole movie about Johnson's character, but the main plot feels a little slighter for it. Still, this is an entertaining indie that isn't so much quirky as it is heartwarming. It genuinely makes you feel good, which is something not a lot of movies this year can claim.