The Monthly Film Bulletin wrote: "Oddly unheralded by producers and distributors alike, Unearthly Stranger is in fact the best British SF-film since Wolf Rilla's Village of the Damned.

One can pick holes in the script – the officially unqueried substitution of bricks for the corpse in Munro's coffin is one of them; but in the long run ingenuity and suspense pay off handsomely.

Julie's abnormality is eerily conveyed in shots of her tear-stained cheeks, furrowed as if by acid, and in little things like her imperviousness to heat as she lifts a red-hot casserole from the oven with her bare hands.

This presented some cinematic obstacles but director John Krish ... kept his small cast on the move within the limited area, cutting to occasional outside scenes for a change of pace.

"[5] In Offbeat: British Cinema's Curiosities, Obscurities and Forgotten Items, Phll Tonge wrote: "Unearthly Stranger is a very odd but rewarding experience.

He also has a field day getting the lighting to turn the good-looking Neville into a pointy-faced freak ... Patrick Newell's performance as Major Clark is nothing short of outrageous.

"Although Unearthly Stranger appears to draw attention to the performance of femininity, it is male society that is the real object of scrutiny," they say, describing it as "a highly effective fable" and praising its "unsettling atmosphere of dislocation and tension which disturbs our taken-for-granted assumptions about the worlds of office and home".

Unearthly Stranger is the most explicit treatment of the Otherness of women in all British SF films, a male-voiced I Married a Monster from Outer Space (1958)".