The New England Aquarium says the 1-pound female lobster has an orange side and a black side, with the colors split perfectly down the middle.
Marine officials say such coloration is estimated to occur once in every 50 million lobsters.
The fisherman who caught the seasonally colored crustacean in a trap last week is from Beverly, a seaside community 20 miles northeast of Boston.
The rare lobster is known as a split. Aquarium officials said Wednesday splits have been caught in Maine, Rhode Island and Nova Scotia in the last 10 years.