Te3n is a remake of the 2013 South Korean film "Montage"

Amitabh Bachchan suggested the director to shoot the film in Kolkata.

It is the first Hindi film for which the doors of the Victorian-era Writers' Buildings were opened for shooting.

Amitabh Bachchan recorded a version of song "Kyun Re" for the film.The song depicts the pain of a grandpa who has lost his granddaughter.

Amitabh Bachchan and Nawazuddin Siddiqui work together for the first time.

Sabyasachi Chakraborty and Vidya Balan appear together after 11 years since they worked in Parineeta (2005).

The media had reported that the film was titled "Kerala" when the film was announced.

Amitabh Bachchan and Sabyasachi Chakraborty appear together after 12 years since they worked in Khakee (2004).

Amitabh Bachchan's name in this movie is John. He previously had his character name John in the film Naseeb (1981).

Sujoy Ghosh was going to direct the film when it was titled " Badla". Naseerruddin Shah was to do the role eventually done by Nawazuddin Siddique.

Vidya Balan made Guest appreance in the movie

Mamata Shankar was offered a role, but things did not work out.

The film released along side of Conjuring 2 and Do Lafzo Ki Kahani.

Although Hum Kaun Hai? (2004) was the last Amitabh Bachchan in which he played a Christian character he made a guest appearance that movie. However, the last movie in which he played a full role as a Christian was Aakhree Raasta (1986).

There is more than one theory as to why the film's title is 'TE3N'. There are three central characters - a grandfather, a priest and a policewoman. The date of the child's kidnapping is 3rd October. In the end, there are only three people who know the truth.

In night scene when the kidnapper is carrying the child the in trunk, he raises the volume of FM Radio to suppress the voice of child. The FM Radio is broadcasting the commentary of final over of India vs. Pakistan Cricket World T20 2007 final match.