Donald J. Irwin, a Norwalk, Conn., Democrat who served three terms in Congress, two years as state treasurer and four years as mayor of his home town, died July 7 at his home in Norwalk. He was 86.

The cause was heart problems, said his wife, Janet Irwin.

Mr. Irwin represented southwestern Connecticut for three terms, from 1959 to 1961 and from 1965 to 1969.

A year after losing his 1960 reelection bid to Republican Abner Sibal, Mr. Irwin was appointed state treasurer by Gov. John Dempsey to finish the term of John Speziale, who left office to become a judge. Mr. Irwin won back the congressional seat in 1964 by beating Sibal and was reelected in 1966.

He lost the 1968 election for the House seat to Republican Lowell P. Weicker Jr., the future U.S. senator and Connecticut governor. Mr. Irwin returned to his law career after the defeat and went on to serve two terms as Norwalk mayor from 1971 to 1975.

Donald Jay Irwin was born Sept. 7, 1926, in Rosario, Argentina, to American parents. His father was a buyer for the American beef firm Swift & Co., according to the Norwalk Hour newspaper.

Shortly after beginning undergraduate studies at Yale University in 1945, he left school to serve in the U.S. Army in Brazil for the Joint Brazil-United States Military Commission.

After his military service, he returned to Yale, earned his bachelor’s degree in 1951 and law degree in 1954 and became a lawyer. He also served on the Norwalk Board of Education before winning election to Congress.