Mercedes Helnwein was born in Vienna, Austria. Her father is Austro-Irish artist Gottfried Helnwein and her mother is Renate Helnwein. She and her brothers, Cyril, Ali, and Wolfgang Amadeus, have often modeled for their father’s work as children. Helnwein and her family live in a castle in Tipperary, Ireland. In 2000, she began dividing her time between Ireland and the U.S. Her studio is located in downtown Los Angeles.

Mercedes Helnwein is "known for large-scale drawings of intrigue and suspense," as reported by Juxtapoz. She also employs ink and paint. New York Magazine describes her work as "immaculately executedlike dramatically lit, attractively cast indie flicks." Helnwein’s art debuted in 2003, with her first group exhibition hosted in Los Angeles by art collector and actor Jason Lee. This exhibition was followed by regular self-instigated one-night-shows at spaces throughout L.A. often with photographer Alex Prager with whom she founded Devils Porchlight Press in 2004. Thereafter, Helnwein began to exhibit in New York, Berlin, Dublin and London.

Mercedes Helnwein contributed art to the Beck album, The Information (2006), and appeared in his music video for "Gamma Ray," filmed by photographer and filmmaker Autumn de Wilde.

She is represented by the following galleries: Blackston Gallery (New York), Merry Karnowsky Gallery (Los Angeles), The Shooting Gallery (San Francisco), Pool Gallery (Berlin), and Bespoke Gallery (Dublin).

Publications that discuss her work include the Los Angeles Times, BlackBook, Los Angeles Confidential, Los Angeles Magazine, Nylon, New York Magazine, New York Art Magazine, i-D, Juxtapoz, The Irish Times, Irish Independent, Berliner Morgenpost (Berlin), Die Welt, Tank Magazine (UK), Blag (UK) Lodown magazine (Berlin), Metal magazine (Spain), and Yodona (Spain).

Damien Hirst acquired the entire work of Helnwein's "Whistling Past the Graveyard" show, presented by A Gallery in London.

Mercedes Helnwein includes video as a medium in her work. Her brother, Ali Helnwein, composed the scores for "East of Eden" as well as "Faking it" and "Whistling Past the Graveyard." The films are reminiscent of the characters depicted in her drawings.

In 2004, her travelogue, “Devil Got Religion,” covered the 15-day road trip with Alex Prager and Beth Riesgraf for their “America Motel” installation.

In 2006, she signed with the literary agency, Ed Victor Ltd., based in London. Other representation includes the New York agencies, Fletcher & Company and William Clark Associates.

Her debut novel, The Potential Hazards of Hester Day, was released in February 2008 by Simon & Schuster. Publishers Weekly reviewed the work of literary fiction as a “funny, offbeat debut novel...[Helnwein’s] soul-searching adventure is reliably entertaining and her obligatory final-page epiphany feels just right.”