The Rev. Msgr. James Edward Malloy, 66, pastor emeritus of Sacred Heart Catholic Church in La Plata, Md., and a former clergyman in Washington, died Saturday at the Sacred Heart rectory. He had cancer and a heart ailment.

Msgr. Malloy had been appointed pastor of Sacred Heart Church in 1968. He was named dean of Charles County, Md., and a member of the Senate of Priests in 1970 by Cardinal Patrick O'Boyle, then archbishop of Washington.

A year later, Father Malloy was elevated to domestic prelate with the title of monsignor by Pope Paul VI. He became vicar for Charles and Calvert counties in 1974.

He was born in Mount Savage, Md. He studied at St. Mary's Seminary in Baltimore and was ordained a priest in 1939 in Washington.

Msgr. Malloy was assistant pastor at St. John's Church in Forest Glen, Md., St. Joseph's Church in Washington, St. Peter's Church in Olney, Md., St. George's Church in Valley Lee, Md., and St. Francis de Sales Church in Washington.

He is survived by a brother, William D., of Washington, and three sisters, Margaret Cole and Helen Malloy, both of Baltimore, and Mary Cina, of Beltsville.