The Los Angeles native died Saturday -- one day after his 71st birthday, People.com said Monday.
The cause of his death was not immediately disclosed.
"I was so sad to hear today of the passing of my dear friend and business associate Frank Bank, who played Lumpy on Leave it to Beaver. He was a character and always kept us laughing. My deepest condolences to Frank's family," Bank's "Beaver" co-star Jerry Mathers posted on Facebook Saturday.
Bank wrote about his experiences working on the iconic TV series in the 1997 autobiography "Call Me Lumpy."