Devlin gradually began writing scripts. His first produced screenplay was for Universal Soldier. He reached prominence as a writer/producer working alongside Director Roland Emmerich, with whom he teamed after appearing in Emmerich's film Moon 44. Together they cowrote and produced Stargate, the first movie to have a web site. The team then produced Independence Day and Godzilla. They split following the 2000 Mel Gibson film The Patriot, but re-teamed to film Independence Day: Resurgence in 2015. Devlin has also produced Cellular, Who Killed the Electric Car?, and Flyboys.