Produced by Guneet Monga, Anurag Kashyap and Arun Rangachari, The Lunchbox is an international co-production of studios in India, the US, Germany and France.

It stars Irrfan Khan and Nimrat Kaur alongside Nawazuddin Siddiqui, Bharti Achrekar and Nakul Vaid in supporting roles.

Ila (Nimrat Kaur) is a young housewife seeking the attention of her husband, Rajeev (Nakul Vaid), and searching for ways to bring the romance back into her marriage; one of her ideas is to cook delicious lunches for him.

Through a rare mix-up of the dabbawalas (complicated food delivery system in Mumbai that picks up and delivers lunches from restaurants or homes to people at work), the tiffin carrier (lunchbox) Ila prepares for her husband gets accidentally delivered, instead, to Saajan Fernandes (Irrfan Khan), a middle-aged widower who is about to retire from his job of an accountant.

Ila eventually realises the mistake and with the advice of her neighbour aunt, Mrs. Deshpande (Bharti Achrekar - voice only), living in the apartment above her, writes a letter to Saajan about the mix-up and places it in the lunchbox (along with her husband's favourite meal) the next day.

After Shaikh reveals that he is an orphan who taught himself accounting, Saajan gradually warms up to him, and eventually the duo strike a close friendship.

At one point, Saajan saves Shaikh's job by covering for his blatant mistakes and becomes the best man at his marriage with Mehrunissa (Shruti Bapna).

Upon receiving an empty lunchbox in disappointment the next day, Saajan writes back to the dejected Ila and apologises to her, stating that he did arrive and watched her from a distance, but could not approach her.

Some time later, Ila's father, battling with lung cancer, dies in the care of her mother (Lillete Dubey), who confesses how unhappy her marriage was.

She writes a farewell message to Saajan announcing that she has decided to leave Rajeev and move to Bhutan with her young daughter, Yashvi.

The film ends with Ila waiting for Yashvi to return from school and Saajan heading to her house with the dabbawalas who regularly picked up and delivered the eponymous lunchbox.

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.

[15] Variety called it "a notable debut from tyro helmer-scripter Ritesh Batra", for creating a film with "crossover appeal of Monsoon Wedding", and also praised acting of Irrfan Khan and Nimrat Kaur.

The website's consensus reads: "Warm, affectionate, and sweet but not cloying, The Lunchbox is a clever crowd-pleaser from first-time director Ritesh Batra.

"[29] Metacritic, which uses a weighted average, assigned the film a score of 76 out of 100, based on 28 critics, indicating "generally favorable" reviews.

[30] Critic Rajeev Masand of CNN-IBN gave a rating of 5/5 to the film stating, "The greatest love stories are the ones that make you root for the protagonists to come together, despite their destinies.

"[31] Pratim D. Gupta of The Telegraph gave two thumbs up to The Lunchbox calling it "as much a moving and muted love story as it is an evocative portrayal of loneliness.

"[32] Taran Adarsh of Bollywood Hungama gave the movie a 4/5 stating, "A well-told old-fashioned romance, The Lunchbox gracefully unknots the trials, tribulations, fears and hopes of everyday people sans the glamour that the city of Mumbai has become synonymous with.

"[37] Suparna Sharma of The Asian Age gave it 4 out of 5 stars and said: "The Lunchbox is a gently pulsating sweet-sad story of loneliness and love, of wilting spirits finding water again.

But it does tick all the boxes that might appeal to festival audiences: quaint Asian urbanism (Mumbai trains, dabba delivery), Indian home-cooking, romance.

"[39] In a less positive review for the Chicago Reader, J. R. Jones criticized the film's premise as a gimmick and its purported use of "irritating comic foil" in reference to Nawazuddin Siddiqui's and Bharati Achrekar's characters as Shaikh and Mrs. Deshpande, respectively.

[41] Director Karan Johar also put his support behind the film saying "All kinds of audience can connect with it and yet within the parameters of love story it is completely unusual.