In order to bring authenticity to the role and for knowing each other well enough to share the love and resentment among the couple as per the story in the film, Nimrat Kaur (Ila) and her onscreen husband Nakul Vaid (Rajeev) stayed at the same house as shown in the movie for weeks and spent days extensively rehearsing their part and adjusting to it prior to the other cast members even getting finalized.
Aged 46 at the time of the movie's release, Irrfan Khan (Saajan) was only seven years older than Nawazuddin Siddiqui, whose character (Shaikh) is the eager young office junior Saajan is training to replace him.
Ritesh Batra, who had made short films, The Morning Ritual, Gareeb Nawaz ki Taxi and Cafe Regular, Cairo, started researching for a documentary on the famous Lunchbox delivery system of Mumbai, dabbawala, known for their efficiency, however after spending a week with them in 2007, he got to know of many interesting personal stories they would overhear while waiting outside an apartment. This idea gave birth to the idea of the film, and instead of making the documentary he began writing a film script.
The three main characters in the film - Saajan (Irrfan Khan), Sheikh (Nawazzudin Siqiui) and Ila (Nimrat Kaur) - all belong to different religions. Saajan is a Christian, Sheikh a Muslim, and Ila is a Hindu. This signifies the unity in diversity existing in the Mumbai City.
India's official entry to the BAFTA Awards, 2015.