Khalil Mufarrij was born in Beirut in 1947 to Dr. Sleiman Mufarrij MD from Broumana, and Mona Youssef Sader from Beirut, the only boy amongst five girls. He went to Broumana High School and got his General Certificate of Education (GCE) in 1966. One of his selected subjects was drawing, but he attended the class only once as he was sure to do well in the exam. He was active in the Scout movement between 1961 to 1966, and became an assistant troop leader. In 1967 / 1968, he received his Baccalaureate I and II from Chouaifat National College.

Khalil joined AUB in 1968 and got his BA in Political Science in 1973. The young idealist Khalil was a committed political activist, an Arab nationalist who felt that the Arab homeland needs revolutionary measures to be modernized and become part of the developed world. He read political party programs and political thoughts including his mother's uncle, Amine Rihani's books, Kings of Arabia and Heart of Lebanon. His ideal was Kamal Ataturk who in an unprecedented manner revolutionized Turkey and carried it into the twentieth century.

At seventeen, following the steps of his uncle, Fouad Mufarrij, who was a well-known Arab National activist, Khalil organized a political movement with his fellow students during his last year in Broumana High School and in Chouaifat College which he called Al Aazm (willpower) Party. At AUB, he co-founded with a few fellow students another politically active group As'hab el Raii (the idea holders), which developed into a wide Student Front movement, nicknamed Al Sana, which established a student co-op and an employment bureau. The movement conducted seminars on campus and in homes, held open-air political sketches and organized trips to south Lebanon in solidarity with the Lebanese on the frontiers under frequent Israeli attacks. All members of these secret movements have later taken senior positions in civic and public life in Lebanon. In 1969, with few fellow students, he joined a hunger strike and refrained from eating for a whole week, surviving on water and fruit juices, when the Israelites raided Beirut airport and destroyed the Lebanese commercial air fleet. At AUB, he tried to take a course in painting and sculpture but had to drop it and take an economics course instead. One semester before graduation, he was diagnosed for Multiple Sclerosis, which changed his life drastically.

But illness did not prevent the dynamic, ambitious young university graduate from pursuing work. After graduation, Khalil worked for half a year at Trans Mediterranean Airways (TMA) in the sales department at the airport and then in the Personnel office. Later, in 1975, he joined Al Hawadeth Magazine and worked for one month, translating documents from English to Arabic, as he had a good style in his mother tongue. His illness and later the civil war interrupted his work.

Khalil loved to travel. He went to Cyprus in 1962, to Egypt in 1964, to Syria, Jordan and Palestine in 1966, to Denmark, Sweden, Norway, Netherlands, England and France in 1970, as well as to London and Paris (1975), to Saudi Arabia (1976), and to the Greek islands (1981).

Khalil tried working in contracting for a while, then travelled to Saudi Arabia for one month, and then decided to go to Greece for vacation and to study the possibility of going into shipping. He also contemplated travelling to the USA to follow his dreams, but the creeping symptoms of his incurable disease worked against his wishes and gradually bound him to his house in Broumana to follow another path, the path of self-discovery through painting.

Khalil's development as a painter was gradual as he was an autodidact. He read extensively; history of art books, conceptual as well as technical books on art. His early works, starting in 1998, were drawings in pencil and colored pens on paper and were mostly portraits. His drawings were personal commentaries, both descriptive and suggestive, but always perfectly coherent, revealing a keen sense of observation. He started using oil pastel in 2001 and in some of his works in 2002. He was prolific from 1998 until 2002, drawing an average of seventeen pieces a year. It fell down to two drawings after that, and only one in 2009, as he did not feel at ease in controlling his pen.

Khalil shifted to acrylic paint on canvas as a vehicle in 2003 in representational, often figurative style. His departure in painting could be an idea, an incident, a subject or a complex reference. Figurations started to disappear gradually in 2006 and his work lost its link with the world of images and became totally abstract in 2009. His abstractions often have a narrative intention that may not be obvious to the viewer.

Khalil does not hesitate to use different painting techniques on his canvas. He applies paint generously with brush, knife, or directly from the tube by dripping, dribbling and pattering, and always in a painterly manner to exploit the visual expressive potential of colors.

The internal dynamism of his paintings is revealed in the viscosity, speed and impact of laying paint on canvas. The act of painting becomes a psychophysical action, a storehouse of dynamic forces. His colors are often loud, exhibiting physical truculence as if he is tackling the chaos of his subconscious to let out his buried impulses, and find himself through the process of painting, until his painting becomes himself.

Some of Khalil's paintings seem to be close to action paintings, where there are neither straight lines nor geometric forms, only the dynamic energy of color. His paintings are expressive, subjective and spontaneous creations. They are emotional responses to his situation: a cultured, intelligent, well-read and informed young man, positive and humane, a free spirit, a gentleman, a prisoner of his body. The painting has become to Khalil like breathing. In the process of painting, he is searching for his own vocabulary, to better express his ideas and feelings about life, the world, and the universe. It is an exhilarating adventure of self-discovery, aiming at and reaching to the true image of his soul.

Along the years exhibitions were held for Khalil, namely at:

A book about Khalil Mufarij's works of art was published and signed by Cesar Nammour at the UNESCO Palace in Beirut on November 18, 2010.

- Galerie Surface Libre, private exhibition, August 2011, Jal El Dib, Jardin Dadour
- Beirut Art book fair, private exhibition, 26 to 29 October 2011, Beirut Souks - Souk El Alwan
- Recto Verso, Solidere, private exhibition, September 26 to October 6, 2012, Saifi Village Beirut
- American University of Beirut, collective exhibition, AUB Alumni Art Expo, West Hall, February 15, 2013
- Silk Valley Resort, 19 to 21 July, 2024, Arbanieh

Some paintings of the artists in his art studio