He married Ramsarni Mehra at the age of 17. The following year, their eldest son Ranbir Raj Kapoor was born, who would later be known as Raj Kapoor. Two more sons followed: Ravinder Kapoor, also known as Bindi, and Devinder Kapoor, also known as Devi.

After completing school in Lyallpur and Lahore, Prithviraj attended Edward College in Peshawar, where he continued to act in theatre. His English professor, Jai Dayal, encouraged him to pursue his passion for acting. After graduating with a degree in Arts, he studied law for a year, but soon gave it up as it held little interest for him. His ambition was to build a career in acting.

With a loan from Kaushalya Bua, a cousin of his father who wished to encourage his dreams, Prithviraj set out from Peshawar for Calcutta. However, en route in Lahore, he changed his mind, bought a ticket to Bombay, and boarded the Frontier Mail. Kaushalya also provided a monthly allowance to support the family of four he had to leave behind in Peshawar.

In Bombay, he made the rounds of theatre companies and managed to meet Ardeshir Irani of Imperial Studios. Irani offered him a job as an unpaid extra in a film titled Challenge (1929). While on set, Prithviraj attracted the attention of Ermeline, the film's heroine. Impressed by his appearance and demeanour, she recommended him for her next film. Irani subsequently hired him as the lead in Cinema Girl (1930), at a salary of 75 rupees per month.

Following the success of Cinema Girl, Prithviraj brought Ramsarni and their three sons to Bombay. The two younger sons, Devi and Bindi, died in quick succession. Devi contracted pneumonia, and Bindi died after accidentally ingesting rat poison.

Soon after, Prithviraj was signed as the lead in nine silent films in rapid succession.

Ardeshir Irani was launching India's first talkie, Alam Ara, and Prithviraj was offered a role. He had been successfully playing lead roles, but the lead in this film had already gone to Master Vitthal, the reigning superstar of the time. Still, it was a challenging part — at the mere age of 25, Prithviraj had to play the father of the heroine, Zubeida, which he accepted gladly. The film was a success, and the arrival of talkies opened up new opportunities for him, thanks to his deep and powerful voice and excelent command over Hindustani, Urdu, and English languages.

On 21st of October 1931, Shammi Kapoor was born.

After two years at Imperial, Prithviraj grew a little restless and began looking for something more creatively stimulating and challenging. He missed theatre, and around this time, he joined James Grant Anderson's theatre company. Anderson was also building the Indian National Theatre in Bombay.

Prithviraj toured several cities with the troupe, performing works by Shakespeare, Bernard Shaw, and Sanskrit plays in English. He was particularly lauded for his Shakespearean roles, especially as Laertes in Hamlet and Shylock in The Merchant of Venice. Actors David Abraham and Durga Khote were also part of the group.

However, after about a year, while they were performing in Calcutta, Anderson had to call off the tour due to lack of funds. Prithviraj chose to stay in Calcutta and joined the burgeoning New Theatres studio of B.N. Sircar.

Prithviraj worked on several New Theatres productions and consolidated his stardom with an eclectic range of films such as Debaki Bose's Seeta (1934) and Rajrani Meera (1933), Pramathesh Barua's Manzil (1936), and Nitin Bose's President (1937) and Dushman (1939). His most notable role from this period was as King Shiva Singha in Debaki Bose's Vidyapati (1937).

However, with the rise of bilingual productions, Prithviraj felt he was being sidelined in favour of Bengali actors. Meanwhile, the Bombay film industry was flourishing. He returned to Bombay with an offer from Chandulal Shah of Ranjit Movietone.

On 18th of March 1938, Balbir Raj Kapoor was born. He would later be known as Shashi Kapoor.

Prithviraj acted notably in A.R. Kardar's Pagal, earning praise for his portrayal of a psychotic doctor. Following this, he broke away from the studio system and became one of the first Indian actors to work as a freelancer.

His first major success as a freelance actor and star was Sohrab Modi's Sikandar, in which Prithviraj portrayed Alexander the Great. The film became a sensation, and his performance remains iconic. His commanding presence and theatrical style eventually played a role in K. Asif casting him as Akbar in Mughal-e-Azam, nearly two decades later.

Debaki Bose's Raj Nartaki, featuring Prithviraj Kapoor, holds the distinction of being the first Indian film produced entirely in English. To widen its appeal among Indian audiences, it was simultaneously filmed in Hindi and Bengali. It was a landmark experiment in multilingual production during the formative years of Indian cinema.

The Indian People's Theatre Association (IPTA) was established, and like many socially committed actors, directors, and writers of the time, Prithviraj was associated with it. However, contrary to popular belief, he was not a founding member and did not direct many significant plays for the group.

Prithviraj established Prithvi Theatre while at the peak of his screen stardom. He involved his son Raj Kapoor, who was now 20 years old, in helping with production, managing backstage, and occasionally acting. One of their major productions during this time was Shakuntala. Prithvi Theatre toured several cities and towns with its plays.

One of the landmark Prithvi productions, Deewar, emerged from conversations between Inder Raj Anand and Prithviraj Kapoor about a story centred on unity, brotherhood, and the ills of British imperialism. Since India was still under British rule, a direct anti-British narrative was not possible. Instead, they devised an allegorical plot about two brothers living together in harmony until a British couple arrives and creates conflict between them, eventually leading to the construction of a wall separating their spaces. Alongside Inder Raj Anand, other notable talents associated with Prithvi Theatres at the time included Shankar Jaikishan and Ramanand Sagar, both of whom contributed to this iconic play.

Released at the height of Prithviraj Kapoor's popularity as a leading man, Vikramaditya (1945) was directed by Vijay Bhatt, known for his period dramas. The film depicted the reign and benevolence of King Vikramaditya and featured Prithviraj in the title role, opposite Prem Adib as the legendary poet Kalidas.

Conceived at the cusp of India's Partition and Independence, Pathan was Prithviraj Kapoor's heartfelt appeal for communal harmony. The play tells the story of a deep friendship between a Hindu and a Muslim family. Prithviraj plays Sher Khan, a Muslim Pathan who sacrifices his own son so that his Hindu friend's son may live. Raj and Shammi Kapoor alternated in the role of the sacrificed son across different shows. The play was well received and remains one of Prithvi Theatre's most critically acclaimed productions of that era.

Awara is one of the most significant examples of Raj Kapoor's humanist cinema of the 1950s. Written by Khwaja Ahmad Abbas, whose socialist leanings are reflected in the script, the story revolves around an upright judge (Prithviraj Kapoor) whose estranged son becomes a petty criminal. A desperate act of murder brings the son to trial in his own father's courtroom. The film brought together three generations of the Kapoor family: Prithviraj Kapoor, his father Basheshwarnath Kapoor, and his sons Raj and Shashi Kapoor.

An adaptation of Bankim Chandra Chattopadhyay's eponymous Bengali novel, Anand Math (1952) portrays the Sanyasi Rebellion, in which Hindu sanyasis of Bengal and Bihar rose in revolt against the British East India Company. Prithviraj Kapoor plays Satyanand, the head of one such group. The film features Lata Mangeshkar's rendition of "Vande Mataram," a song that had its origins in Bankim's novel. The music was composed by Hemant Kumar.

Prithviraj Kapoor got to play the role of a lifetime as Akbar the Great in the 1960 magnum opus Mughal-e-Azam. K. Asif had originally cast the actor Chandramohan as Akbar when he had prepared to make Mughal-e-Azam in the 1940s, but after the demise of Chandramohan he was back to square one. When the film was being cast afresh, he could think of no one better than Prithviraj Kapoor to take up the mantle. His stature and voice were a perfect fit for the role. Prithviraj completely surrendered to Asif's vision and his screenplay to breathe life into the role. It was widely acclaimed and remains one of the best performances of Indian cinema.

Zindagi, a Ramanand Sagar film produced by Gemini Pictures in Madras, featured Prithviraj Kapoor as a law officer once again. He plays a jury member in the trial of a man accused of murder, when the son of his estranged wife testifies that he was with the accused on the night of the crime. Rajendra Kumar, Raaj Kumar, and Vyjayanthimala co-starred.

K. A. Abbas directed Prithviraj Kapoor in a film called Aasman Mahal, written by Inder Raj Anand. He played a Nawab who resists the conversion of his haveli into a hotel. Much like Satyajit Ray's Jalsaghar (The Music Room), the story explored the decadent decline of feudalism. Prithviraj's performance won him an award at the Karlovy Vary Film Festival.

In the same year, he played the noble King Porus (Puru) in Sikandar-e-Azam (1965).

The films that followed included Nanak Naam Jahaz Hai (1969), the Ramsay Brothers' early horror film Ek Nannhi Munni Ladki Thi (1970), his grandson Randhir Kapoor's directorial debut Kal Aaj Aur Kal (1971), and a Kannada film titled Sakshatkara (1971), in which he played the father of superstar Dr. Rajkumar.

Diagnosed with Hodgkin's disease, Prithviraj passed away on May 29, 1972.