Ehrlichman died Sunday of natural causes at his home in Atlanta. He had suffered from diabetes, his son Tom said Monday.
Ehrlichman, one of Nixon's two top advisers along with H.R. Haldeman, resigned from his White House post in April 1973. He was convicted two years later for obstruction of justice, conspiracy, and perjury in the attempted cover-up of the burglary of the Democratic National Committee offices at the Watergate complex in Washington.
To outsiders he was widely seen as arrogant, sarcastic and an unblinking Nixon loyalist, reports CBS News Correspondent Eric Engberg.
When Mr. Nixon complained about the leak of secret documents, it was Ehrlichman who set up the "Plumbers", a team of burglars, to gather dirt on presidential enemies.
As the cover-up began to unravel and pressure mounted, Nixon summoned Haldeman and Ehrlichman to Camp David, Md., in April 1973 and told them they would have to resign.
The next day, he fired White House counsel John Dean, and accepted the resignations of Haldeman, Ehrlichman and Attorney General Richard Kleindienst.
Ehrlichman spent 18 months at Swift Trail Camp, a minimum-security federal prison south of Safford, Ariz., and was released in 1978. Haldeman also served 18 months in prison and died in November 1993.
Ehrlichman was born March 20, 1925, in Tacoma, Wash. He graduated from UCLA and received a law degree from Stanford University in 1951.
During World War II, he was a lead navigator in the 8th Air Force, earning the Air Medal clusters and the Distinguished Flying Cross. Before working at the White House, he was a partner in the Seattle law firm of Hullin, Ehrlichman, Roberts & Hodge from 1952 to 1968.
After getting out of prison, Ehrlichman moved to Santa Fe, N.M., where he began a new career as an artist, writer and commentator. He wrote four novels and a memoir Witness to Power: The Nixon Years.
But none of the dialog would become as famous as Ehrlichman's own advice to Nixon on how to get rid of a new FBI director stained by Watergate: "Just let him twist there, slowly in the wind."
He eventually moved to Atlanta to serve as senior vice-president of Law Environmental.
He is survived by his wife, Karen Hilliard, four sons, two daughters and his mother. Funeral services will be private.