Copper naphthenate is most widely used in wood preservation and for protecting other cellulosic materials such as textiles and cordage from damage by decay fungi and insects.

Other metal naphthenates are used as paint driers, rubber adhesion promoters, lubricant additives, and catalysts where oil solubility is required.

In addition to broad efficacy against decay fungi and wood-destroying insects, its low mammalian toxicity is a key reason why copper naphthenate has gained market acceptance as a proven effective wood preservative that is specified and used extensively for environmental reasons by utilities and railroads as a less toxic alternative to creosote, pentachlorophenol and arsenicals in poles, crossties and bridge timbers.

Consumer methods of application include dip, brush or spray; specific directions for use are found on the pesticide label on the container.

The color of CuN-treated wood may vary from light brown-green to dark brown depending on the type of oil and the treating process.

Copper naphthenate is also used as the antimicrobial active ingredient and drying agent in FDA-approved hoof thrush treatments for horses.

[7] The antimicrobial properties of copper compounds have long been exploited as pesticides due to their broad activity against a variety of decay fungi and wood-destroying insects, including termites.

[8][9] Copper naphthenate, when used as a preservative for wood and other cellulosic materials such as cotton fabric and cordage, is by definition a pesticide and thus must be registered with the U.S. Environmental Protection Agency (EPA).

Copper naphthenate is classified by EPA as a general use (i.e., a non-restricted use) pesticide by virtue of its relatively benign toxicity profile.

[5] Copper naphthenate is the only non-restricted use wood preservative in widespread use for "heavy duty" commodities such as utility poles, railroad crossties and timbers, pilings and fence posts.