Johnson won the Writers Guild of America (WGA) Award for Best Dramatic Series for her work on Lost.

In fall 2004 Johnson joined the crew of Lost as a co-producer and writer for the first season.

She co-wrote the episodes "The Moth" (with story editor Paul Dini) and "Whatever the Case May Be" (with series co-creator and executive producer Damon Lindelof).

Johnson and the writing staff won the WGA Award for Best Dramatic Series at the February 2006 ceremony for their work on the first season.

In September 2011, Johnson was brought on to the FOX mystery series Alcatraz, as executive producer and co-showrunner (along with Daniel Pyne).