Leno left the show in 2009 , and Conan O'Brien ( of Late Night and Saturday Night Live fame ) became host from June 2009 to January 2010 before leaving due to controversy with The Tonight Show 's timeslot . Jay Leno became the host of the show again on March 1 , 2010 . After Leno 's run as host of The Tonight Show , Conan O'Brien took over as host .