Moria concludes their 2 star (out of 5) review with this:
Considering the torrid stew of elements, the film emerges with more of a staidness than it ever seems to promise. On the plus side, the colour contrasts are rich and full and Gordon Hessler directs the killings with reasonable style.1000 Misspent Hours calls the script "bewilderingly stupid" and Price's performance "one of his most tasteful and understated," says Lee's "talents are almost totally wasted here" and concludes:
During its first half hour, I had high hopes for The Oblong Box. But as the film progressed, those hopes gave way to an escalating sense of dismay as it became increasingly clear that not enough remained of the film’s running time to answer any of the questions that would make sense of the story.Stomp Tokyo says, "The Oblong Box manages to make voodoo curses, vengeful maniacs and premature burials paradoxically languid and diffuse." Rotten Tomatoes gives it a score of 57%.