One of the few Bollywood movies not to have any singing in it.
Based on the English film Signpost to Murder (1964), it was adapted into a screenplay in seven days, shot in 28 days and released in a record three months. The director had wanted a inexpensive quickie film as his big budget film Aadmi Aur Insaan (1969) had stopped production because it's heroine Saira Banu was having surgery.
Ittefaq was the last film Yash Chopra directed for his brother's BR Films.
It was remade in 2017 with the same name directed by Abhay Chopra, B R Chopra's grandson.
Yash Chopra wanted Raakhee to play heroine but she was under contract with the Rajshri's for her first movie Jeevan Mrityu. Nanda who had costarred with Khanna in The Train was signed for the role.