Priscilla L. Buckley, a journalist who was the longtime managing editor of National Review, the conservative magazine founded by her brother William F. Buckley Jr., died on Sunday at her home in Sharon, Conn. She was 90.

Her death, at Great Elm, the 30-room Georgian mansion in which Miss Buckley and her siblings were reared, was of kidney failure, said her nephew Christopher Buckley, a writer and Mr. Buckley’s son. Miss Buckley had lived for many years in one of the several condominiums into which Great Elm was partitioned in the 1980s.

Miss Buckley, who was associated with National Review for more than four decades, was its managing editor from 1959 to 1985. In that role, she oversaw the day-to-day operations of the magazine, riding herd — by all accounts without raising her voice so much as a decibel — on a staff of occasionally bibulous, sometimes fractious and constitutionally dilatory writers....