Sylvia Deaton began her dance training at the Diana Evans School of Dance in Lexington and as a scholarship student at the Otto M. Budig Academy of Cincinnati Ballet. In 2005, Deaton became a trainee with Boston Ballet School studying as a Sydelle Gomberg Scholarship recipient for two years. In addition, she attended Boston Ballet's Summer Dance Program as a scholarship student for three years training under Margaret Tracey, Deidre Miles Burger, Celia Marino, Jacqueline Cronsberg, Parren Ballard, and Kathleen Mitchell. She joined Boston Ballet as a member of Boston Ballet II in 2008 and as a member of the company in 2010.
In 2007, Deaton competed in the Tanzolymp Festival in Berlin, Germany, receiving a silver medal. She also attended an exchange program with the Royal Danish Ballet that culminated in a performance of August Bournonville's Flower Festival in Genzano. Deaton attended the Festival Dance program at the Banff Centre in Alberta, Canada, receiving the Alice Schultz Scholarship. She was Boston Ballet's Princess Grace nominee for 2011. Referring to 2012's Barber Violin Concerto, the Hub Review stated that Deaton "proved a particularly appealing free spirit...grabbed her big chance with both hands...and made the biggest splash of all."
Deaton's Boston Ballet repertoire includes Mikko Nissinen's The Nutcracker and Swan Lake, Peter Martins' Barber Violin Concerto, Herald Lander's Etudes, Florence Clerc's version of Petipa's La Bayadère (Manu), Maina Gielgud's Giselle (Lead Willi), Don Quixote (Cupid), Sir Frederick Ashton's La Fille mal gardée, George Balanchine's A Midsummer Night's Dream (Lead Butterfly), Coppélia (Spinner), Divertimento No. 15 (Variation #1), Ballo della Regina (soloist), Jewels, Symphony in Three Movements, The Four Temperaments, Symphony in C (Fourth Movement demi soloist), Serenade (Russian Girl), and La Valse, August Bournonville's La Sylphide, Marius Petipa's The Sleeping Beauty (Songbird, pas de trois, Little Red Riding Hood), John Cranko's Romeo and Juliet (Clown), Jiří Kylián's Falling Angelsand Symphony of Psalms, Jorma Elo's Plan to B, Sharper Side of Dark, Lost by Last, Double Evil, Carmen, and Awake Only, and William Forsythe's The Second Detail.