Massasoit was the title, Great Sachem, of Ousamequin, leader of the Pokanoket and the Wampanoag tribes. He held the allegiance of seven lesser Wampanoag sachems. He visited Plymouth in 1621 and negotiated a treaty guaranteeing the settlers their security in exchange for their alliance against the Narragansett, an alliance needed by Massasoit because the Wampanoag had been so decimated by European disease brought by English settlers.

He forged important personal ties with English settlers such as Stephen Hopkins, Edward Winslow and William Bradford that helped maintain good relations during his lifetime.

Massasoit's oldest son, Wamsutta , became sachem of the Pokanoket on the death of his father. He began using English names for himself ("Alexander") and for his brother, Metacomet ("Philip"), who succeeded him on his death in 1662.

The only child of Massasoit to survive King Philip's War was his daughter, Amie, wife of Tispaquin .