Born into a musical family in Mococa, São Paulo, Brazil, Sergio Assad began creating music for the guitar not long after he began playing the instrument. He learned Brazilian folk melodies from his father. By age 14, he was arranging and writing original compositions for the guitar duo he had formed with his brother, Odair. At the age of 17, he and Odair began their studies under the best known classical guitar teacher in Brazil at the time, Monina Tavora, a former disciple of Andrés Segovia. Sergio later went on to study conducting and composition at the Escola Nacional de Música in Rio de Janeiro, and worked privately with Brazilian composition teacher, Esther Scliar.
Over the last twenty years Assad has concentrated most of his efforts on building a repertoire for the guitar duo. He has extended the possibilities of the two-guitar combination through his arrangements of Latin American music by composers such as Piazzolla, Villa Lobos, and Ginastera as well as Baroque to Modern music by Scarlatti, Rameau, Soler, Bach, Mompou, Ravel, Debussy, and Gershwin among others. He has completed over 300 arrangements for different chamber music settings arrangements for Gidon Kremer, Dawn Upshaw, Yo Yo Ma, Nadja Salerno-Sonnenberg, TrioConBrio, Iwao Furusawa, Paquito D'Rivera, Turtle Island String Quartet, L.A. Quartet, Luciana Souza, and Vancouver Cantata Singers.
As a composer Assad has completed more than fifty works for guitar, many of which have become standards in the guitar repertoire. His "Aquarelle" for solo guitar was chosen as the required contemporary work for the 2002 Guitar Foundation of America Competition in Miami. In 2007, he wrote the set piece for the 2008 Guitar Foundation of America Competition named "Valsa de Outono". Assad’s orchestral compositions include the ballet "Scarecrow", the concerto "Mikis" for guitar and strings, "Fantasia Carioca" for two guitars which he and Odair premiered with the Saint Paul Chamber Orchestra in 1998, "Interchange", a concerto for guitar quartet and orchestra premiered by the Los Angeles Guitar Quartet with the San Antonio Symphony in 2009, the concerto "Originis" for violin, guitar duo, and orchestra recorded live with the Orquestra Sinfônica do Estado de São Paulo, and the concerto "Phases" for guitar duo and orchestra premiered in 2011 by the Seattle Symphony Orchestra with the Assad Brothers as soloists.
Assad has taught master classes in conservatories, universities, and music schools in the US, Europe, Latin America, Japan, and Australia. From 1994 to 1996, he taught at the Conservatoire Royal de Musique in Brussels and from 2003 to 2006 at the Chicago College of Performing Arts at Roosevelt University. He is currently on faculty at the San Francisco Conservatory of Music.