Ishikawa grew up in Washington state. He was selected in the 21st round of the 2002 Major League Baseball Draft by the San Francisco Giants out of high school and made his major league debut with the team in 2006. He started 2009 as the Giants' first baseman. On defense he was third in the National League in fielding percentage. In 2010, he earned a World Series ring as part of the Giants' World Series victory.