There are three major lineages of marine mammal strains of Brucella spp.: Brucella ceti ST23, found predominantly in porpoises; B. ceti ST26, in pelagic delphinids and ziphiids; and Brucella pinnipedialis ST24/25, predominantly in seals. The isolation of Brucella spp. in mysticetes has been described only in common minke whales (Balaenoptera acutorostrata) in Norway and Scotland. We report a third case of Brucella infection and isolation in a minke whale associated with a large abscess. In contrast to the two previous reports that involved isolates of B. pinnipedialis ST24 or the porpoise-associated B. ceti complex ST23, this case was associated with the dolphin-associated B. ceti ST26. Thus, minke whales can be infected naturally with members of all the distinct major lineages of Brucella associated with marine mammals. This report is unique in that the B. ceti ST26 did not originate from a pelagic delphinid or a beaked whale.