Epsilon has hosted and managed National Geographic's enterprise marketing database, which now contains more than 45m members, consumer and prospect records, since 1997.
The society also uses Epsilon's permission-based email and information targeting services.
Dave Wasdahl, vice president of marketing services at National Geographic, said: "With such a vast membership base and multiple channels of communications, managing our database platform ensures we can connect with our key audiences.
"Epsilon has played a significant role in our marketing strategy both on the database and email side, and we're pleased to continue investing in our relationship."
The National Geographic Society is non profit-making and reaches more than 360m people each month through its magazines, the National Geographic TV channel, television documentaries, music and radio, films, books, DVDs, live events and interactive media.