A court ruled in favour of Playtex in the case, which dates back to 2003. The original trial, which ran for nine days, saw Playtex awarded $3m in damages and banned Procter & Gamble from making any further comparative claims in its advertising.
Now the Second Circuit Court of Appeals has upheld the original ruling, meaning that the injunction and award still stand.
The case surrounded advertising claims for Pearl tampons, made by P&G, saying that they were superior to Playtex's Gentle Glide tampons.
Neil DeFeo, president and CEO of Playtex, said: "Playtex is pleased by the court's decision. We look forward to continuing to compete with P&G in the marketplace. This is a great day for all the Playtex employees who worked so hard to ensure that our Gentle Glide tampons are second to none."
Other brands owned by Playtex include Wet Ones and Mr Bubble bubble bath. It is owned by Sara Lee Corporation.
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