Mengering was well-known to her son's audience as a part of the cast of the recurring characters who appeared often on his NBC show "Late Night" and his CBS "Late Show", reported Variety.
A spokesperson for Letterman confirmed that Mengering died on Tuesday, a day before the host's 70th birthday.
Mengering was born on July 18, 1921 in Indiana's Linton as Dorothy Hofert and she married Harry Letterman, David's father in 1942.
She had three children with Harry - Jan, David and Gretchen.
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Mengering first appeared on "Late Night" in the year 1986. She also made frequent return visits leading up to Thanksgivings and Mother's Days on the series.
An excellent pie-maker, one of her most popular recurring portions with her son was "Guess Mom's Pies".
Mengering also served as a "Late Show" correspondent at three successive Winter Olympics in 1994, 1998, and 2002.
She also published a cookbook with writer Jess Cagle, titled, 'Home Cookin' With Dave's Mom' in the year 1996.