Stone appeared in three films released in 2009. The first of these was opposite Matthew McConaughey, Jennifer Garner and Michael Douglas in Mark Waters' Ghosts of Girlfriends Past. Loosely based on Charles Dickens' 1843 novella A Christmas Carol, the romantic comedy has her playing a ghost who haunts her former boyfriend. Critical reaction to the film was negative, though it was a modest commercial success. Her most financially profitable venture that year was Ruben Fleischer's $102.3 million-grossing horror comedy film Zombieland, in which she features alongside Jesse Eisenberg, Woody Harrelson and Abigail Breslin. In the film, she appeared as a con artist and survivor of a zombie apocalypse, in a role which Empire's Chris Hewitt found to be "somewhat underwritten." In a more positive review, The Daily Telegraph's critic wrote, "[T]he hugely promising Stone ... [is] a tough cookie who projects the aura of being wiser than her years." Stone's third release in 2009 was Kieran and Michelle Mulroney's Paper Man, a comedy-drama which disappointed critics.
Disillusioned at being typecast as the "sarcastic interest of the guy", Stone co-starred with Viola Davis in Tate Taylor's period drama The Help (2011), a film she found challenging. The film is based on Kathryn Stockett's 2009 novel of the same name and is set in 1960s Jackson, Mississippi. She met with Taylor to express a desire to work in the film. Taylor has said: "Emma was completely awkward and dorky, with her raspy voice, and she sat down and we got a little intoxicated and had a blast, and I just thought, 'God! God! This is Skeeter." She was cast as Eugenia "Skeeter" Phelan, an aspiring writer learning about the lives of the African-American maids. In preparation for the part, she learned to speak in a Southern accent; she also educated herself on the Civil Rights Movement through literature and film. With a worldwide gross of $216 million against a budget of $25 million, The Help became Stone's highest-grossing film to that point. The film, and her performance, received positive reviews from critics. Writing for Empire, Anna Smith thought that Stone was "well-meaning and hugely likable" despite finding flaws in the character. The film was nominated for an Academy Award for Best Picture, and won Best Ensemble Cast from the Women Film Critics Circle and the Broadcast Film Critics Association.
Stone moved from Los Angeles to Greenwich Village, New York, in 2009. In 2016, she moved back to Los Angeles. Despite significant media coverage, she has refused to speak about her private life. Concerned with living a "normal" life, Stone has said that she finds little value in media attention. She has expressed her fondness for her profession, and has cited Diane Keaton as an acting influence, calling her "one of the most covered-up actresses of all time". She has also named Marion Cotillard as one of her inspirations.
Stone has been described as a style icon—the media cites her hair, eyes, and husky voice as her trademarks. Vogue credits the actress for her "sophisticated, perfectly put-together looks", writing that "her charisma, both on-screen and off-, has charmed many." In 2009, she featured in AskMen's Top 99 Women, FHM's 100 Sexiest Women in the World, and Maxim magazine's Hot 100; the latter also placed her on the list on three other occasions—2010, 2011, and 2014. She continued to be featured in AskMen's annual beauty lists from 2010 to 2015, ranking among the top forty each year. In 2011, she appeared in Victoria's Secret's list of What is Sexy? as the Sexiest Actress. She was mentioned in several other media outlet lists that year, including People magazine's 100 Most Beautiful Women, each of FHM's and FHM Australia's 100 Sexiest Women in the World, and Men's Health magazine's 100 Hottest Women. She ranked sixth on Empire's list of the 100 Sexiest Movie Stars in 2013. Stone was named the best dressed woman of 2012 by Vogue magazine and was featured in similar listings by Glamour in 2013 and 2015, and People in 2014. In 2017, Buzznet named her one of the world's most beautiful women.