"Heaven got a great comedian and actor today," his daughter Michele said in a statement.
Of Uncle Leo, Lesser told the Los Angeles Times in 1998: "He's the kind of guy who is a total nuisance at times and the kind of guy you avoid. He's a very expansive character, and that has an attraction to it."
The New York native, who graduated in economics and government from City College in 1942 before serving in the Army during World War II, started his acting career in 1954 and appeared in the movies Birdman of Alcatraz, Kelly's Heroes, Papillon and Clint Eastwood's The Outlaw Josey Wales."
Besides the 1989-98 Seinfeld, other TV shows featuring Lesser included Get Smart, The Munsters, The Rockford Files, ER and Everybody Loves Raymond, on which he played a Leo-esque character named Garvin, a lodge brother of Raymond's father Frank (Peter Boyle).
Reports say Lesser, a father of two, was divorced in 1982 after 28 years of marriage.