Warner joined PDI/DreamWorks in 1997 to serve as a producer on the computer animated hit Antz, which marked the first collaboration between PDI and DreamWorks. Warner went on to become head of PDI/DreamWorks from 2000 to 2002. Warner had previously held the post of vice president of production at Twentieth Century Fox, where he supervised production on such films as Independence Day, The Ice Storm, The Crucible, Alien Resurrection and Titanic.
A graduate of UCLA Film School, Warner started out as a production coordinator at Empire Pictures, gaining experience on low-budget horror and science-fiction films. He then moved on to a position at Film Finances, a completion bond company, where he worked on more than 50 films.