Castellane, 61, said his decision to leave was influenced by a close brush with death two years ago from a heart attack and, more recently, by the sudden death of a friend, the Nassau County Legislature's presiding officer, Peter Schmitt (R-Massapequa), who died in October of a heart attack.
"He never got a second chance," said Castellane.
He said his post-retirement plans are to enjoy life and spend more time with his wife and a 1965 Ford Mustang he recently bought.
The council is composed of representatives of 36 construction union locals covering workers on Long Island and in New York City.
Castellane, a Vietnam War veteran, said he has been active in unions for about 40 years, starting as a construction laborer, then becoming a representative and organizer for Local 12 of the International Association of Heat and Frost Insulators and Allied Workers.
He became president of the council in 2007, succeeding John Kennedy, who had held the post for decades until his death that year.
Castellane's successor is to be chosen in a special election Jan. 9, with about 150 representatives of the 36 locals voting.
At Castellane's recommendation, he said, the council's executive board has endorsed iron worker Richard O'Kane, 63, business manager of Iron Workers Local 361.