In 1955 the Spanish poet Jaume Ferran put her in contact with leading writers of the 1950s, such as the Ferrater brothers, Jaime Gil de Biedma, Carlos Barral, Juan Goytisolo, and Josep Maria Castellet. She then began working as a correspondent in Barcelona and doing part-time work at the ACER literary agency, owned by the Romanian writer Vintilă Horia. Later Horia moved to Paris, which led her to found the Carmen Balcells Literary Agency in 1956. The agency started with the management of translation rights to foreign authors. Later, the first local author she represented was Luis Goytisolo. This was followed by a long list of prominent authors such as Pablo Neruda, Gabriel García Márquez, Mario Vargas Llosa, Julio Cortázar, Miguel Delibes, Alvaro Mutis, Camilo José Cela, Vicente Aleixandre, Gonzalo Torrente Ballester, Manuel Vázquez Montalbán, Jose Luis Sampedro, Terenci Moix, Juan Carlos Onetti, Jaime Gil de Biedma, Carlos Barral, Josep Maria Castellet, Juan Goytisolo, Alfredo Bryce Echenique, Juan Marsé, Eduardo Mendoza, Isabel Allende, Rosa Montero, Gustavo Martin Garzo.
Some authors, such as García Márquez, Marsé, Onetti, Tosar and Dourado, have dedicated novels to her; others, such as Max Aub, Vázquez Montalbán, Donoso and Barral have included her as a character in their work.
Balcells considers her great accomplishment to be revising the contracts between authors and publishers to be more fair to authors. She established time limits on contracts and reserved the rights of translations for the authors.
One day, by phone, García Márquez asked, "Do you love me, Carmen?" She replied, "I can not answer, you are one third of my revenue."
With almost forty years of work under her belt, Balcells announced in May 2000 that she was retiring as a literary agent. She had received the Gold Medal of Fine Arts and was invested with an honorary doctorate from the Universidad Autonoma de Barcelona (UAB). Her literary agency became headed by Gloria Gutierrez. However, in 2008 she returned again to take charge of the agency since it lost important writers such as Guillermo Cabrera Infante and Roberto Bolaño, who left to be with the agency of Andrew Wylie, known in the publishing industry as "el Chacal"; also the loss of authors such as Luisge Martin and Daniel Vázquez Salles.
In 2010 the Spanish Ministry of Culture bought approximately fifty years of her personal archives for three million euros.
In May 2014 Balcells announces she will join with Andrew Wylie to become the Balcells-Wylie agency.
Eldest of four children, she was born on August 9, 1930 into a family of small landowners in Santa Fe de Segarra, Les Oluges, Lleida, Catalonia, Spain, a small town of only fifty people. She attended primary school in her hometown. In 1946 she moved with her family to Barcelona, where she did various jobs not related to literature.
In 1961 she married Luis Palomares, with whom three years later she had her only son, Luis Miguel Palomares Balcells, who is, since 2016, the owner and director of the agency.
As the most famous literary agent in the world of Spanish letters she has received numerous awards, among them the following:1997 – Medal of Honor in Barcelona.
2000 – Medal for Artistic Merit, awarded by the City Council of Barcelona.
2005 – Doctor Honoris Causa from the Autonomous University of Barcelona.
2006 – the Cross of Saint George.
2006 – Montblanc Award for Women.
She is on the Advisory Council of the Prince of Girona Foundation.