Dubbed ArnoldEleven, the New York-based venture will serve clients seeking the creative expertise of an image-focused fashion boutique and the resources of a creative shop, the agencies said.
So far, Arnold has identified about 10 creatives and executives that will lend their services to ArnoldEleven, but will tap into additional agency talent based on client needs, said Lynn Power, exec VP at Arnold Worldwide.
Under the deal, the two agencies will share client fees; other terms were not disclosed.
The move represents an effort by Arnold, whose clients in the apparel space include Lee Jeans, Timberland and Talbots (which earlier this month went into review, but the agency plans to defend), to tap into upscale marketers.
Founded in 1988 by Giovanni C. Russo, No. 11's portfolio includes work for H. Stern, Moet & Chandon, Ralph Lauren, Victoria's Secret and designer Yohji Yamamoto.
"Arnold is a terrific partner to provide us with business-strategy expertise and integrated communications across all media," Mr. Russo said in a statement. "I look forward to this partnership as a way to grow both of our agencies' capabilities and client rosters."
ArnoldEleven has signed on online retailer RedEnvelope, San Francisco, as its first client.
"Big agencies aren't always a great fit for a retailer, but the flip side of that is that creative boutiques sometimes follow their own creative vision instead of staying true to the customer or brand," RedEnvelope's chief marketing officer, Scott Sanborn, said in a statement. The blend of the two embodied in ArnoldEleven represents a "perfect fit" for the online retailer, Mr. Sanborn said.