Tim Sullivan moved to Los Angeles where he worked in development at New Line Cinema, co-producing Detroit Rock City (1999) (1999) with Gene Simmons of KISS and current Warner Brothers Chairperson and former classmate Michael De Luca. Sullivan's mainstream directorial debut was the well-received LionsGate's horror-comedy 2001 Maniacs (2005) (2005), produced by Eli Roth. This was followed by Driftwood (2006) (2006), 2001 Maniacs: Field of Screams (2010) (2010), and Chillerama (2011) (2011). Sullivan gained additional notoriety as celebrity director of Vh1's hit series Scream Queens (2008) (2010) (handpicked by James Gunn to succeed him). Under his own production banner New Rebellion Entertainment, Sullivan will produce the psychological thriller Lullaby, to be directed by M.J. Bassett ( Reacher (2022)) , along with the romantic comedy A Boyfriend for My Wife) , also written by Sullivan.

Sullivan was previously married to Originals Film head Tania Landau (De Luca and current Universal president Donna Langley served as best man and maid of honor respectively).