Sister Mary Isabel Sullivan, R.S.M., 99, a member of the Sisters of Mercy of the Americas Mid-Atlantic Community for 81 years, died Sept. 29 at Maria Regina Residence in Brentwood, L.I.

She attended Blessed Sacrament School, Cypress Hills, and Bishop McDonnell D.H.S. in Crown Heights, before entering the Mercy Sisters’ Novitiate, Syosset, L.I., in February, 1937. She professed her final vows in September, 1942.

She taught at St. Patrick, Williamsburg, 1939-40; St. Brigid, Bushwick, 1940-42; St. Agatha, Cobble Hill, 1942-51; St. Gregory, Crown Heights, 1951-53; St. Therese of Lisieux, East Flatbush, 1953-58; and Holy Innocents, Flatbush, 1958-61.

She was principal of St. Patrick’s, Bay Shore, L.I., 1961-67, and school supervisor, 1967-75.

She served as assistant to the administration of the Sisters of Mercy Leadership Team, 1975-78, and worked in the field of immigration with the Catholic Migration Office in the Brooklyn Diocese, 1978-94, until she retired.

Sister was also well known for making mitres, having handmade more than 100 in her lifetime.

Her works donned the heads of Bishops Anthony Bevilacqua, Thomas V. Daily and Nicholas DiMarzio, as well as Auxiliary Bishops Raymond Chappetto and Paul Sanchez.

A Mass of Christian Burial was celebrated in the Sisters of Mercy Convent, Whitestone.

Burial was in St. Charles Cemetery in Farmingdale, L.I.