[15] She started collecting vintage clothing at age 15[16] and later attended the Massachusetts College of Art in Boston, where she took architecture classes,[17] and obtained her bachelor's degree in interior and graphic design.

[18] While paying her way through college[7] by waitressing,[7] she held internships at the design firms Cambridge Seven Associates in Boston and Milton Glaser in New York.

While working as a hostess at a Beverly Hills restaurant in 1994, she was scouted by a Playboy photographer and was featured as September Playmate of the Month under the name Kelly Gallagher.

"[7] With apartments filled with pieces from modernist artists such as Arne Jacobsen, Eero Saarinen and George Nelson,[20] The New York Times would write a decade later that "her playful, elegantly over-the-top designs for the Avalon Beverly Hills changed the look of boutique hotels around the world.

[25] Elle Decor would later write that "her luxury hotel interiors" featured "elegant bergère chairs, unexpected lacquer finishes (glistening lemon yellows, Amazon parrot greens) and old-style stately wallpapers.

"[28] HarperCollins published Wearstler's Domicilium Decoratus in 2006, a style book featuring photographs of her Beverly Hills mansion and herself dressed in evening gowns.

"[18] With filming starting in 2006, she served as one of three primary judges on Top Design, a reality show contest that premiered on Bravo in January 2007.

[17] Wearstler appeared in all twenty episodes[17] before the show's end in 2008,[18] and attracted a fair degree of attention in the press with the outfits she wore while judging.

[1] In July 2007 Wearstler opened her first brick and mortar retail space in the form of a boutique[29] in Bergdorf Goodman's home-furnishings department,[7] and the following year her office was based in West Hollywood on La Cienega Boulevard.

[7] By 2009 she had designed the top suite of the Las Vegas Hard Rock Hotel and a home for Stacey Snider of DreamWorks, and was in the process of decorating a large contemporary house for Gwen Stefani and Gavin Rossdale.

[7] Wrote the Los Angeles Times about the book, "Hollywood glamour, neoclassical ornamentation, pattern and texture prove to be Wearstler signatures, but color, she writes, 'is everything.

"[33] The Wall Street Journal called her ready-to-wear clothing and jewelry "reflections of her modern, but also classic and opulent, aesthetic,"[15] while magazine W described that season's fashion collection as "a bold mix-and-match collection of hand-painted blouses, cropped jackets, full-legged pants, and pouf skirts," as well as "stone-laden metal clutches and sculptural jewels" for accessorizing.

[34] As of July 2011 her home furnishing,[18] clothing and accessories continued to be sold at Bergdorf Goodman, as well as through Neiman Marcus, Holt Renfrew, Net-a-Porter,[15] and her website.

[15][33] Her new fashion collection debuted at those same stores in August 2011,[15] and was shortly afterwards sold through a new flagship boutique she opened on Melrose Avenue on September 1, 2011.

Keeps of the Los Angeles Times dubbed the store "a sleek atelier where Art Deco meets 1970s Minimalism and the 1980s Italian style known as Memphis.

[9] Wearstler explained that the book is about combining varied textures, scales, and time periods, opining that mixing "antiques, vintage and contemporary design pieces and art" leads to a more "soulful" interior.

"[43] Wearstler was announced as interior designer for a number of upcoming Proper Hotel properties, including locations in Los Angeles, San Francisco, Santa Monica, Brooklyn, Miami, Napa Valley,[43] and Austin, Texas.

[32] She continued to operate her Los Angeles boutique as of July 2015, with Architectural Digest writing at the time that the store "showcases the breadth and daring of her creative output.

Victor, and Pickard China,[32] and as of 2015 she designed collections of fabrics, wall coverings, and trims for Lee Jofa, before also being sold at her boutique, website, and other stores.

[46][57] In 2018, Wearstler also debuted her first retail project design, a chocolate shop in Los Angeles called Compartés Chocolatier, created in partnership with Jonathan Graham.

[66] In 2020, Wearstler overhauled a house on Malibu's Broad Beach that was believed to have been built by Frank A. Garbutt, co-founder of Famous Players–Lasky, which later became Paramount Pictures.

[69] In March 2021, Wearstler also designed a virtual garage to commemorate the launch of GMC's Hummer EV, which she said was imagined for LeBron James.

[75] In June 2022, Wearstler also became an angel investor in the startup Vergo, a Fintech company that caters to the architecture, design and building industry.

"[80] In 2020, Domino Mag said her toolbox of trademarks included "peacock green and brass, painterly geometric prints, warm marble, slick lacquer, standout vintage from Ettore Sottsass to Tobia Scarpa, and—always—the earthy naturalism of her West Coast home.

"[7] Mayer Rus, the design and culture editor for Los Angeles Times Magazine, stated that "I think for many people around the world Kelly's work exemplifies this fantasy of beautiful sun-baked life, glamour in California.

[15] As an interior designer, Wearstler finds influence in Modernism and old Hollywood glamour as created by Dorothy Draper and William Haines.

[34] Jacque Grange is cited as her favorite designer, in part for "the way he puts things from different periods together so beautifully,"[13] and she also names David Hicks, Mark Rothko, Ettore Sottsass, Misha Kahn,[84] and Piero Fornasetti[20] as among her aesthetic influences.

[18][21] The family has remodeled and sold a number of houses in Southern California,[7] including the former Beverly Hills estate of film producer Albert Broccoli, which they moved into and renovated in 2007.

[39] Wearstler is active on social media, and in early 2014, Architectural Digest included her on a list of 15 Must-Follow Designers and Architects on Instagram.