Hiraman (Raj Kapoor) is a rustic villager, a bullock cart driver, from a remote village in Bihar. Hiraman takes two vows based on difficult situations in his life. He then meets and befriends Hirabai, a nautanki dancer. In the end, Hiraman takes a third vow.

Hiraman has traditional and conservative values. While smuggling illegal goods on his bullock cart and narrowly escaping the police, Hiraman takes a vow (the first kasam) to never again carry illegal goods. Subsequently, while transporting bamboo for a timber trader, Hiraman's load upsets the horses of two men. The two men then beat Hiramam. After this, Hiraman takes a second vow (the second kasam) to never again carry bamboo in his cart.

One night, Hiraman is asked to carry Hirabai (Waheeda Rehman), a nautanki dancer, as a passenger to a village fair forty miles away. As they travel together, Hiraman sings to pass the time and tells Hirabai the story of the legend of Mahua. As the journey progresses, Hirabai is mesmerized by Hiraman's innocence and his simple philosophy of life. Hiraman sees Hirabai as an angel of purity.

Once they reach the village fair, Hiraman joins his band of bullock cart drivers and Hirabai joins the nautanki company. Hirabai asks Hiraman to stay at the village fair for a few days to see her dance. Hirabai arranges free passes for Hiraman and his friends to see the nautanki on every night for the duration of the fair.

As Hiraman attends the nautanki, he becomes aware that other people see Hirabai as a prostitute and this disturbs him. He tries to shield and protect her from society. As the days pass, the bond between Hirabai and Hiraman grows stronger. When Hiraman becomes involved in fights with local people who disparage Hirabai and her profession, Hirabai tries to make him understand that it is the harsh reality of her life. Hiraman asks Hirabai to leave her profession and to start living a respectable life. Hirabai refuses to leave. Feeling depressed, Hiraman leaves the village fair and returns to his village.

Hirabai meets Hiraman and tells him her secret that she had been sold and she was not a virgin beauty and then leaves. Hiraman then takes a third vow (teesri kasam) that he will never again carry a nautanki company dancer in his cart.

• Raj Kapoor, Hiraman
• Waheeda Rehman, Hirabai
• Dulari, Hiraman's bhabhi (sister in law)
• Iftekhar, Vikram Singh
• Keshto Mukherji, Shivratan
• A.K. Hangal, Hiraman's older brother
• Asit Sen,mela announcer
• C. S. Dubey,birju
• Shailendra

Phanishwarnath Renu who wrote the original short story Mare Gaye Gulfam in 1954, also wrote the script. The screenplay was written by Nabendu Ghosh, whose works include Devdas (1955), Sujata (1959) and Bandini (1963). Basu Bhattacharya directed the film with a sense of realism and natural style. He felt it was important for the film that Raj Kapoor should avoid his usual "simple man" mannerisms.

The film took many years to complete. Most of the film was made at Aurahi Hingna, a village in Araria district and Bina, a town near Bhopal, Madhya Pradesh. A few scenes were filmed at Powai Lake and at the Mohan Studios in Mumbai. Subrata Mitra, the cinematographer on Satyajit Ray's early films, had moved to Mumbai for a brief period to make Merchant Ivory films.^[9] The theatre actor A. K. Hangal, knew Shailender from IPTA theatre group days, and agreed to play the small role of Hiraman's elder brother. However, eventually much of his role was deleted in the final editing to reduce the length of the film.^[7]

• Basu Bhattacharya, director
• Phanishwar Nath Renu, story and dialogue
• Nabendu Ghosh, screenplay
• Shailendra, producer
• G. G. Mayekar, editor
• Subrata Mitra, cinematographer
• Desh Mukherjee, artistic director
• Pandit Shivram, costume
• Lachhu Maharaj, choreographer
• Shankar Jaikishan, director of music
• Hasrat Jaipuri, Shailendra, lyricist
• Asha Bhosle, Manna Dey, Suman Kalyanpur, Lata Mangeshkar, Mubarak Begum, Mukesh, Shambhu-Shankar (qawwal), playback singers.

All lyrics written by Shailendra & Hasrat Jaipuri; all music composed by Shankar-Jaikishan.

The film was received well and took the National Film Award for Best Feature Film, however, commercially, it was a failure. Bhattacharya turned to middle cinema (a meeting of mainstream Bollywood and art house cinema). In time, the film came to be regarded as a classic. ^[10][11]

Both leads received acclaim for their acting, while critics felt that Raj Kapoor delivered one of the most sensitive performances of his career, after Jagte Raho (1956).^[12]

A chapter titled 'Teesri Kasam Ke Shilpkar Shailendra' (The Architect of Teesri Kasam Shailendra) (Devnagari: ????? ??? ?? ???????? ????????) which is based on the film is included in CBSE class 10 Hindi Course- B textbook sparsh.

• 1967 National Film Award for Best Feature Film ^[10]
• 1967 Moscow International Film Festival: Grand Prix - Nominated