The final scene of the so-called "American" version of this movie had Barbara and Anne Morton waiting for Guy to call on the telephone. Sir Alfred Hitchcock wanted the phone in the foreground to dominate the shot, emphasizing the importance of the call, but the limited depth-of-field of contemporary movie camera lenses made it difficult to get both phone and women in focus. So Hitchcock had an oversized phone constructed and placed in the foreground. Anne reaches for the big phone, but actually answers a regular one. Hitchcock explained that "I did that on one take, by moving in on Anne so that the big phone went out of the frame as she reached for it. Then a grip put a normal-sized phone on the table, where she picked it up."
Some posters showed Sir Alfred Hitchcock inserting the letter "L" into the word "Strangers" in the title to make "Stranglers".
In the scene where Ruth Roman and Patricia Hitchcock are watching the tennis match, Ruth gives Patricia a real U.S. ten dollar bill. Showing real U.S. money in movies then was illegal without permission from the U.S. Treasury Department. The Treasury Department later removed the prohibition for Psycho (1960) and later movies.
The stunt where the man crawled under the carousel was not done with trick photography. Sir Alfred Hitchcock claimed that this was the most dangerous stunt ever performed under his direction, and he would never allow it to be done again.
As was his usual practice, Sir Alfred Hitchcock shot each scene so that there was only one way to edit it, which always conformed to his initial visual concept and pre-production storyboards.
Alfred Hitchcock: can be seen early in the film, boarding a train carrying a double bass as Guy disembarks.