Decker produced and directed her first short film, Naked Princeton, in 2005.
In 2008, Decker co-directed the documentary Bi the Way with Brittany Blockman, which focused on bisexuality in the United States. Despite being described by Variety's Joe Leydon as a "once-over-lightly examination of an alleged cultural phenomenon", the film nevertheless went on to win the Alternative Spirit Grand Prize at the Rhode Island International Film Festival.
Decker wrote and directed her second short film, Where Are You Going, Elena?, in 2009. In 2012, Decker wrote and directed the short film Me the Terrible, which was praised by Richard Brody of The New Yorker as a "wondrous short film."
Decker has also appeared as an actor in many independent films, including Joe Swanberg's Uncle Kent, Onur Tukel's Richard's Wedding, Saturday Morning Mystery, the romantic tragedy Loves Her Gun, and Stephen Cone's critically lauded drama film Black Box in 2013.
In September, 2014, it was announced that Butter on the Latch and Thou Wast Mild and Lovely had been picked up for a theatrical and VOD distribution by Cinelicious Pics with a planned release set for November, 2014.
In November 2015 Decker served on the Jury of the 33rd Torino Film Festival. The Italian festival had already paid tribute to her work in the Onde section of 2014 edition.
Decker’s third feature film, Madeline’s Madeline, screened at the Sundance and Berlin Film Festivals in early 2018. The film features Molly Parker and Miranda July, and introduces 19-year-old Helena Howard as a troubled acting student whose "class exercises become increasingly immersive and personal".
