Kathryn Louise Habecker Duncan, an ordained minister of the Church of Christ (Disciples) who served for 12 years as a missionary in Tibet, died Thursday in the Fairney-Keedy Memorial Home for the Aged in Boonsboro, Md. She was 84.

Mrs. Duncan, a former resident of Northern Virginia, was born in Sanborn, N.Y. She graduated from Hiram College in Hiram, Ohio, in 1819, and taught school in Indiana from 1919 to 1920.

With her husband Marion, who died earlier this year, she served as a missionary in Tibet from 1921 to 1933. After their return they lived in Ohio until 1941, when they moved to Fairfax County.

In 1946, Mrs. Duncan went abroad again to teach in a Christian mission school in Tokyo, Japan. The Duncans returned here and moved to Alexandria in about 1951. In 1954, they went to Hong Kong for a year, where Mrs. Duncan taught.

During the time she lived in Virginia, Mrs. Duncan was active in volunteer church work. She was a member of the First Christian Church of Alexandria.

In about 1963, Mrs. Duncan and her husband moved to Berkeley Springs, W. Va.For the past few years, however, Mrs. Duncan had lived in Boonsboro.

She is survived by a brother, Leon Habecker of Silver Spring; two sisters, Frances Larsen and Gertrude Hersee of Michigan; two sons, John, of Alexandria, and Robert, of Vienna, Va., two daughters, Marian Adams of Hagerstown, Md., and Esteher Dunker of Pekin, Ill., 12 grandchildren and one great-grandchild.