Xavier Castellanos was born and raised in Geneva, Switzerland. He started painting at the age of four, later attending private painting workshops. He and his family moved to Mexico City, where he had his first solo show at the age of fifteen. After a series of very successful exhibits, he won public acclaim and admission into the Mexico City art circle. His works are held in numerous private and corporate collections. His talent has received recognition from many of the masters of Mexican art, including José Luis Cuevas and Raul Anguiano.

Xavier moved to New York City in 1991 to study Fine Art Painting at The Art Students' League, where he spent four years. His credits since 1988 include more than 50 solo exhibits and more than 70 group shows in the United States, Mexico, and Europe. He now divides his time painting between Mexico and San Francisco. While growing up in Geneva, he visited many European cities and their museums, a number of which he has revisited in the last 15 years. He has also traveled to Egypt, Morocco, Turkey, Japan, Thailand, Cambodia, and Singapore.

Xavier and his relatives have lived in Frida Kahlo's Coyoacan neighborhood, which to this day remains "a Frida Kahlo reference set". Castellanos has a personal interest in Frida Kahlo which began in his early youth. As a child, he visited Kahlo's Casa Azul and her works made a strong and lasting impression. He went on to read most books about Frida and her work, soon becoming a "Frida expert". In 1991, he met relatives of Frida Kahlo, including her niece and her grandniece Cristina. He also met Juan Coronel Rivera, grandson of Diego Rivera. They all remain friends to this day. Castellanos had a chance to interview them as well as some of Diego's cousins and other contemporaries of Frida. Consequentially his interest and expertise about Frida Kahlo increased considerably.

In 1995 Xavier won the competition "Art of the XXth Century" organized by the Louis O. Palmer Gallery at Muskingum College in New Concord, Ohio. He was awarded a prestigious grant by the National Fund for Culture and the Arts of Mexico in 1994.

He worked as a curator and coordinator for the 1992 exhibit "Passion for Frida" at the Mexican Museum of San Francisco; two of his paintings were included in this exhibit. He also presented a lecture entitled "Frida Kahlo and Mexican Art" at the UC Berkeley International House.

One of Xavier's paintings was reproduced on French telephone cards by Schlumberger to commemorate the issuance of their 100 millionth card in 1991. The same year he was commissioned to do the set, poster, and program design for the play "13 Rue de l'Amour" at the South Street Theater in New York City. His works have been selected for juried exhibits at the Davis Art Center (1996) and the Gallery House in Palo Alto (1995).