DeMaine was accepted for study at the Juilliard School in New York City, the Curtis Institute of Music in Philadelphia, and was also invited to learn privately with Pierre Fournier in Geneva, Switzerland, but his parents made the decision that he should complete his secondary education at home.

His many teachers include Steven Doane, Felix Galimir, Luis Garcia-Renart, Paul Katz, Aldo Parisot, Leonard Rose, Joseph Silverstein, and János Starker.

In 2012, Robert DeMaine was named Principal Cellist of the Los Angeles Philharmonic by Music Director Gustavo Dudamel.

In his late teens, DeMaine became the teaching assistant to Steven Doane, and later Paul Katz, at the Eastman School of Music.

As soloist with orchestra, he has collaborated with many renowned conductors, including, John Williams, Gustavo Dudamel, Joseph Silverstein, Leonard Slatkin, Alexander Schneider, Walter Hendl, Neeme Järvi, and Zubin Mehta.