John A. Kopsidas, 79, owner of the old Kopsidas Wholesale Fruit Co. here for 40 years, died Monday at Sibley Memorial Hospital following a heart attack.

Mr. Kopsidas was born in Karia on the island of Lefkanos in Greece. He came to the United States in 1918, and lived and studied in Boston for four years before moving to Washington. He began his wholesale fruit business in 1922 and operated it until his retirement in 1962.

He was a founder of Saints Constantine and Helen Greek Orthodox Church in Washington and was a vice president and member of its executive board. He also was a member of the American-Hellenic Educational Progressive Association and was a founder of the Lefkadian Society.

Mr. Kopsidas made frequent trips to Greece and maintained the family church, St. John's, in his hometown of Karia. The building was erected in 860 and in 1962 was declared an archeological monument by the Greek government. He maintained a home in Karia as well as homes in Washington and Chesapeake Beach, Md.

Survivors include his wife, the former Marion Calomiris, of the homes; a daughter, Margot Phillips, of Chicago; a son, Stephen, of Beltsville; two sisters, Killiops S. Aravanis and Sohpia G. Haramogli, both of Lefkada, Greece, and four grandchildren.