In a December 24 lawsuit filed in the Omaha, Nebraska, federal court, ConAgra said Dean's use on labels of the word Swiss, a snowy white-and-blue mountain scene, and a particular font are likely to confuse shoppers into believing the teas are endorsed by ConAgra.
Such confusion is heightened by the similarity in sight and sound of the parties' respective trademarks as well as the fact that the respective products are both marketed in the beverage category, ConAgra said.
The Omaha-based company said it has sold Swiss Miss products since 1990, with sales topping $150 million annually.
Marguerite Copel, a Dean spokeswoman, declined to comment, saying the Dallas-based company had not been served with the complaint.
ConAgra is seeking to block Dean from using the Swiss Premium label, as well as triple damages and other remedies.
Other ConAgra products include Banquet and Healthy Choice dinners and Orville Redenbacher popcorn.
In morning trading, ConAgra shares fell 16 cents to $23.16, and Dean shares rose 9 cents to $18.17.
The case is ConAgra Foods RDM Inc. v. Dean Foods Co, U.S. District Court, District of Nebraska, No. 09-00465.
(Reporting by Jonathan Stempel, editing by Dave Zimmerman)