Duff launched her clothing line, “Stuff by Hilary Duff”, in March 2004, with clothes distributed through Target in the United States, Kmart in Australia, Zellers in Canada, and Edgars Stores in South Africa. The company, initially started as a clothing line, has expanded its business into furniture, fragrances, and jewelry, targeted at the teen and preteen crowd. In 2007, the Internet website Stardoll.com previewed Duff’s clothing line to customers by allowing them to dress up a paper doll on the website (which include Hilary Duff’s own doll) with the clothes.

In February 2009, Duff and DKNY Jeans announced their new design partnership and the launch of their collaborative apparel line. Duff co-designed a collection of special pieces with DKNY Jeans brand called Femme for DKNY Jeans. The clothing line will debut in fine department and specialty stores nationwide in August 2009.

Playmates Toys released a celebrity doll of her in 2004. In late 2006, Mattel released a Hilary Duff Barbie doll. As a fashion designer, she had designed clothes for Barbie dolls in the past and with the release of her doll, she joined Reese Witherspoon, Beyoncé Knowles, and Lucille Ball who have their own celebrity dolls.

In September 2006, Duff released her perfume, “With Love… Hilary Duff”, which was distributed by the Elizabeth Arden company. The perfume was initially sold only in Macy’s in the U.S. and soon it was being sold in other regions like Japan and Canada. “With Love…Hilary Duff” was one of the three best-selling fragrances launched at U.S. department stores in late 2006. In 2007, Duff announced that she will be releasing a summer version of the perfume titled, “Wrapped With Love”. It was released in January 2008, and a Spring Gift Set version was released in time for Valentine’s Day.

Duff and her pet dog Lola made an appearance in the Electronic Arts game The Sims 2: Pets, which was released on October 2006. In console versions of the game, Duff’s character visits public areas and allows the players to let their Sims socialize with her and Lola. Animal rights’ organization, “Animal welfare league” have criticized Duff and celebrities such as Paris Hilton and Jessica Simpson for displaying their dogs as fashion accessories rather than pets.