In December 1997, GoTo.com began using the logo of a green circle on a yellow background with the letters "GoTo" in white.
Nearly two years later, Disney began using a logo of a green traffic light in a yellow case with "Go" written in white to link its various Websites under the Go Network heading.
In February, GoTo.com sued Disney and Infoseek Corp, the entertainment company's Internet partner, saying the Go Network emblem confuses consumers.
U.S. District Judge Terry Hatter agreed Friday, issuing a preliminary injunction that forces Disney to change its logo.
Hatter said GoTo.com has demonstrated that its claim is merited and that confusion with Disney's logo will cause the firm to "suffer irreparable harm."
Despite the similar titles of the Websites, GoTo.com only argued against the resemblance of the logos, not against the name Go Network.
After GoTo.com files a $25,000 bond Monday, Disney will be prohibited from using the Go Network emblem.
Disney officials said they will fight to retain the company's original logo when the matter goes to trial next spring.
"We are very disappointed in the court's ruling," Disney said in a statement. "We are confident or logo does not impinge on that of any other (company.)"
Disney has spent millions of dollars advertising the Go Network logo since it was created in January.
The traffic light image appears on numerous Disney products and advertising, including movie trailers, theme park Websites and promotions for television networks ESPN and ABC.
GoTo.com executives praised the ruling, saying it will benefit both companies by ensuring customers know who they are doing business with.
"Without the confusion, our advertising dollars are better spent, and the impact of the advertising is more valuable because people know it's us and not Disney," GoTo.com Chief Executive Jeffrey Brewer said.
The ruling comes in the week GoTo.com prepares to launch a new national advertising campaign and Disney is expected to complete its acquisition of Sunnyvale-based Infoseek.
Infoseek, one of the Internet's top search engines, is responsible for most of Go Network.