The son of a barber and a homemaker who were Greek immigrants, he was born and raised in Weirton, W. Va., where he graduated in 1938 from Weir High School.
In the late 1930s, he moved to Baltimore and took a job working for the Baltimore & Ohio Railroad. He enlisted in the Army in 1942 and completed his training at Fort Devens, Mass.
From 1943 until 1945, when he was discharged, he served with the 3608th Quartermaster Truck Company in Africa and Italy, where he drove for the famed "Red Ball Express."
In 1945, Mr. Nopulos and a brother and sister opened Alpha Lunch on Frederick Road in Catonsville.
Mr. Nopulos and his brother, Angelo, then opened the Double T Diner, which they owned and operated until 1987, when they sold the business.
Family members said politicians and celebrities alike visited the restaurant to dine on such dishes as stuffed flounder and crab cakes. The diner was open 24 hours a day, seven days a week.
After the brothers couldn't find the keys to lock up the Double T one Christmas, they never locked its doors again, family members said.
Mr. Nopulos was known for his generosity toward the homeless and donating food to his church, the Greek Orthodox Cathedral of the Annunciation.
He was also a member of the Lord Baltimore Chapter of the American Hellenic Educational Progressive Association.
Mr. Nopulos later owned and operated Kosten's Bar in West Baltimore and the Black Lantern in Westminster, which he eventually sold.
The longtime Bloomsbury Avenue resident enjoyed vacationing at a second home in Ocean City.
He was a member of Rolling Road Golf Club. He was a longtime Baltimore Colts season ticket holder and attended numerous Indianapolis 500 races.
His wife of 45 years, the former Despina "Dessie" Klavas, who also worked at the diner, died in 1991.
Services will be held at 11 a.m. Friday in the chapel of the Greek Orthodox Cemetery, 5917 Windsor Mill Road.
Surviving are a son, Paul Nopulos of Clarksville; two daughters, Claudia McBrien of Ellicott City and Deanne van Velsen of Catonsville; a brother, Angelo Nopulos of Arbutus; three sisters, Sophia Taylor of Manchester, and Rose Arnautis and Mary Keffalos, both of Warren, Ohio; and four grandchildren. Another son, James Nopulos, died in 2008.