Born in Hamilton, Ohio, Beaver graduated from Oberlin College and Cornell University (Ph.D., 1933, history). He went to China in 1938 as a missionary of the Evangelical and Reformed Church. After language study in Peking, he taught at Central China Union Theological Seminary in Ling-ling, Hunan Province, from 1940 to 1942. He was interned in Hong Kong by the Japanese for seven months until repatriated in 1943.
Beaver taught missions at Lancaster (Pennsylvania) Theological Seminary from 1944 to 1948, then was director of the Missionary Research Library (MRL) at Union Theological Seminary, New York City, from 1948 to 1955. In 1955 he was appointed professor of missions at the University of Chicago Divinity School, where he taught until his retirement in 1971. After retirement he was director from 1973 to 1976 of the Overseas Ministries Study Center, then located in Ventnor, New Jersey. He was a founding member of the Association of Professors of Missions in North America in 1952, serving as its president from 1956 to 1958, and for many years he was a trustee of the Foundation for Theological Education in South East Asia.
Beaver's greatest contributions to missiology were through research and writing, as well as his encouragement of other scholars through his teaching and professional associations. During his tenure at MRL he began publication of the Occasional Bulletin from the MRL (later the International Bulletin of Missionary Research, published by the Overseas Ministries Study Center), which provided documentation and encouraged scholarship in studies of Christian missions.
Among his numerous publications were several pioneering studies that became standard references, especially Ecumenical Beginnings in Protestant World Mission: A History of Comity (1962) and All Loves Excelling: American Protestant Women in World Mission (1968; rev. 1980). He edited The Gospel and Frontier Peoples (1973) and a large symposium for the American Society of Missiology in 1976, American Missions in Bicentennial Perspective, which one reviewer described as "a landmark in the development of missiology in America." On the occasion of his retirement from the University of Chicago, a Festschrift was presented to him, The Future of the Christian World Mission: Studies in Honor of R. Pierce Beaver. In 1972 he received an honorary D. D. from Concordia Seminary, Saint Louis, Missouri. He died in Tucson, Arizona.