The film premiered at the 2002 Toronto International Film Festival, It also received a strong reception when screened at the San Francisco International Film Festival in 2003. The film received high critical acclaim upon release and went on to win six National Film Awards, six Filmfare Awards South, seven Tamil Nadu State Film Awards and Best Film awards at six international film festivals.
The film begins in a small village in Sri Lanka called Mankulam, where M. D. Shyama (Nandita Das) is married to Dileepan (J. D. Chakravarthy), who along with few other Sri Lankan Tamils in the village, is part of the Tamil Tigers rebel association. While having a quiet moment, the couple hears sounds of Sri Lankan army troops approaching. He asks Shyama to leave while he remains in the forest. Shyama realizes that she is pregnant and waits in vain for Dileepan’s return. Her villagers begin fleeing to India to seek refugee due to the war. Shyama is initially stubborn to leave her husband behind, but her relatives convince her to seek refuge for her unborn child's sake. The villagers board a boat to the shores of Rameswaram. On the journey one of the rebels says that he has seen her husband, Dileepan, with bullet wounds in the forest. Shyama wants the boat to turn around but it is too late. In Rameswaram, while a local collector takes down the names of the refugees, Shyama gives birth to a baby girl. However, the urge to find her possibly wounded husband and be with her people back home overwhelms Shyama and she leaves behind the newborn girl, hoping that the girl will lead a better life.
Nine years later in Chennai, a young girl, Amudha (P. S. Keerthana) narrates about her family life. She introduces her father, writer Thiruchelvan (R. Madhavan), who uses the pen name 'Indira' for his books. Indira (Simran Bagga) is Amudha's mother, while she has a younger brother named Vinay and another younger brother called Akhil. Amudha's ninth birthday approaches and both of her parents take her to the temple. Indira later reminds Thiruchelvan of their promise to reveal 'the truth' to Amudha on her ninth birthday. After their prayers, Thiruchelvan brings Amudha to Marina Beach and reveals the truth that she was adopted from a refugee camp in Rameswaram and is not their biological daughter. Amudha is heavily disturbed after hearing the news and begins distancing herself from the family. Indira's father criticizes them for revealing the truth to her, but Thiruchelvan and Indira are certain they have taken the right decision. Amudha asks her foster-parents about her adoption.
The film then flashes to nine years ago in Rameswaram, where Thiruchelvan, then a budding writer, constantly travels to the refugee camp and writes stories inspired by the people there. At one such instance, Thiruchelvan sees a newborn baby girl, and writes a short story about the girl. Indira is his neighbour, and has always expressed an interest in him. Thiruchelvan, after a while, finds the urge to adopt the girl, but realizes that he will not be allowed to do so until he is married. He then proposes to Indira in order to be able to adopt the baby. Indira suggests the name 'Amudha' after seeing the baby once, and then adopt the baby after they marry each other. Vinay was born few years after their marriage, followed by Akhil, and thus, the family happened.
Even after hearing this, Amudha is dissatisfied. She requests to meet her mother despite Indira's insistence that they can't possibly find her even if they wanted to. Thiruchelvan gives in and promises to take Amudha to Sri Lanka to find her mother. Leaving the two boys under the care of Indira's father, the trio travel to Sri Lanka and are greeted by Dr. Herold Vikramasinghe (Prakash Raj), who also helps them to find Amudha's mother. Amudha and Indira's relationship strains as Amudha becomes increasingly rude at her mother while urging to find her real mother. While taking a walk in the jungle, Thiruchelvan and Vikramasinghe are captured by a group of LTTE rebels. Thiruchelvan immediately recites Tamil poetry and is identified as Indira by the group's leader (Pasupathy). Thiruchelvan explains his motives of coming to the country, mentioning the only evidence that he has regarding Amudha's mother is that her name is Shyama. The group leader arranges a meet and says he will bring Shyama to the spot. It is later revealed that Shyama is the group leader's sister who is also a part of the LTTE rebels living in seclusion.
The next day, Vikramasinghe, Amudha, Indira, and Thiruchelvan wait at the spot, but a sudden series of bombings break out at the place as the Sri Lankan army tries to infiltrate the hideout of the rebels. Indira gets shot in her arm in the process. The family finally leaves the place, and Amudha, apologizes to Indira and asks all of them to return to India. The next day, the family leaves for the airport but unexpectedly, Indira requests that they drive through the meeting spot one more time. As they wait, Shyama arrives. Amudha asks Shyama a series of questions, which Shyama is unable to answer, but she finally says that her life would be dedicated to fighting for her people in her country and that Amudha should live happily with her adopted parents and leaves.
The film ends with Thiruchelvan, Amudha, and Indira hugging each other as Shyama leaves, and a teary-eyed Amudha kisses her parents, re-affirming her love for them.Madhavan as Thiruchelvan ( pen name "INDIRA")
P. S. Keerthana as T. Amudha
Simran as Indira Thiruchelvan (Voice dubbed by Deepa Venkat )
Nandita Das as M. D. Shyama (Voice dubbed by Sukanya )
Prakash Raj as Dr Herold Vikramasinghe
J. D. Chakravarthy as Dileepan (Voice dubbed by Thalaivasal Vijay )
Delhi Kumar as D.Ganesan
Easwari Rao as Shyama
Bala Singh as Devanathan
M. S. Bhaskar as Shankaralingam
Pasupathy as Pasupathy
Kamala Krishnaswamy as Kamala
Sashikumar as the suicide bomber
Siddharth in an uncredited cameo
Shefali Chowdhury as an uncredited refuge
Like other Mani Ratnam projects, the film began production with very little official publicity in early 2001 with the media covering the project as either Manjal Kudai (Yellow Umbrella) or Kudaigal (Umbrellas). The film was reported of a trilogy of films based on love and peace in the backdrop of war - after Roja (1992) and Bombay (1995) - with Mani Ratnam choosing to base the film with the backdrop of the Sri Lankan Civil War. Madhavan was signed up to play a leading role in the film, with the venture becoming his third straight Mani Ratnam project after Alaipayuthey and the Mani Ratnam production, Dumm Dumm Dumm. For the role of Indira, Mani Ratnam considered casting either Rani Mukerji, Soundarya or relative newcomer Bhumika Chawla, before finalising Simran to portray the character. Madhavan and Simran thus shot for two films simultaneously together, as they had also been cast in K. Balachandar's Paarthale Paravasam as a married couple. Nandita Das was also roped in for the film, making her debut in Tamil films, and in a later interview mentioned that the team shot for nearly thirteen hours a day. P. S. Keerthana, the second daughter of actors Parthiban and Seetha, was cast the child artiste in the film, while Prakash Raj was also roped in to play a Sinhalese character. Mani Ratnam approached actor Vikram to make a special appearance as Keerthana's biological father in the film, but his refusal meant that J. D. Chakravarthy was later handed the role.
The title of the film was finally announced as Kannathil Muthammittal (A peck on the cheek) in July 2001, after a famous phrase from a poem written by Subramanya Bharathi. Parts of the film shown to be Colombo in the film were shot in Puducherry. Further schedules were carried out in the forests of Kerala to depict the base of the LTTE in northern Sri Lanka. As most of the cast were non-native Tamil speakers, dubbing artistes were used with actresses Sukanya and Deepa Venkat lending their voices for Nandita Das and Simran respectively. Furthermore, Mounika lent her voice for Easwari Rao's character, while Thalaivasal Vijay spoke lines for Chakravarthy.
The film has won the following awards since its release: