The move returns Apple's board to seven members, the number it had before Edgar Woolard Jr. stepped down earlier this year. Apple's corporate structure, however, remains unusual in that the company has had no chairman for several years.
Apple chief executive Steve Jobs, who analysts say clearly is running the show even if he is not officially chairman, offered praise for the new addition to Apple's board.
"Art is a highly respected CEO and leads one of the most important and successful science-based companies of our time," Jobs said in a statement. "We look forward to his insight and counsel as a member of Apple's board."
Jobs, who had been Apple's interim chief executive since 1997, became the permanent CEO in January. Genentech, a biotechnology company, is based in South San Francisco, Calif.