The Avatar actress will appear in the FX biker drama's sixth season, Entertainment Weekly reports.
Her character Tyne Patterson is a San Joaquin district attorney who gets involved with bike gang SAMCRO.
Sons of Anarchy was created by writer Kurt Sutter, who previously worked with Pounder on FX cop drama The Shield.
The 60-year-old actress will follow in the footsteps of fellow Shield veterans Jay Karnes, Walton Goggins, Benito Martinez, David Rees Snell and Kenny Johnson, who have also appeared on Sons.
Sutter revealed late last year that the show will likely wrap after seven seasons.
"Season seven was always my goal because I know how this cable model works," he explained. "I've always had that number [of seasons] in my head."
Season six of Sons of Anarchy will premiere on FX on September 10.
> Sons of Anarchy prequel a possibility, creator reveals at Comic-Con
Watch a promo for Sons of Anarchy's fifth season finale below: