The actors, who both star on the ABC sitcom Cougar Town, were photographed together at the beach in St. Bart's on Wednesday.
News outlets including TMZ have suggested that Cox and Hopkins are dating.
However, a spokesperson for Cox told E! News that their relationship is "strictly platonic", explaining: "Courteney is there with Josh, Coco and some other good friends."
An insider close to Cox earlier insisted to Gossip Cop that the actress is vacationing in St. Barts and that the two stars are "not dating".
Cox, who recently revealed that she wished Friends continued after its final season, separated from husband David Arquette last October.
Cox and Arquette have reportedly been seen together in public recently near their home in Malibu.