Gertrude Tannen
Biographical information
Date of birth1883
Age (1885)2
Age (1931)48
Age (1955)72
Age (1985)102
Physical description
Hair colorGray
Eye colorGreen
Behind-the-scenes information
Played byThomas F. Wilson (voice only, uncredited)
Gertrude Tannen sign

Marty McFly spots Gertrude Tannen's name above the door of the Tannen residence through binoculars.

"The front door opened and Biff walked out. / "Biff!" the elderly woman's voice called from inside the Tannen house. "Where are you going, Biff?" / Biff started to walk quickly away from the house. / "To get my car, Grandma!" he called over his shoulder. / "But when are you coming back, precious?" his grandma whined. "My feet hurt, and I want you to rub my toes some more. And put polish on them!" / Biff waved violently back at the house. / Marty called back to Doc on the walkie-talkie. "Never mind, Doc. Biff lives here all right." "
—From Back to the Future Part II by Craig Shaw Gardner (quote, pages 141 and 142)

Gertrude Tannen was Biff Tannen's grandmother, Irving "Kid" Tannen's mother, Tiff Tannen and Biff Tannen Jr.'s great-grandmother, and presumably Buford "Mad Dog" Tannen's daughter-in-law.

Biff was her only grandson, but in an alternate timeline, where Kid Tannen didn't go to jail, she was also the grandmother of Clifford and Riff.


Gertrude was known to be an extremely unpleasant woman, and did not seem to encourage visitors. This was supported by the fact that a large handwritten sign at the gate of the Tannen residence read NO TRESPASSING / VIOLATORS WILL BE PROSECUTED / THIS MEANS YOU!!, while a handwritten sign reading KEEP OFF THE GRASS! was also stuck into the front lawn.


Gertrude was born in 1883 in Hill Valley, California.[1] Sometime before 1907, she married the son of Buford Tannen, a famous outlaw who killed twelve men in 1884, not including Native Americans and Chinese men.[2] And they had a two son's Frank Tannen (born 1907) and Kid Tannen (born 1909).

In 1937, she took custody of Biff, because neither her son Kid Tannen or daughter in law Myra Benson wanted him. She isn't shown on-screen, but only heard from inside the house where she yells at Biff — making her sound abusive and mean, which is likely the reason why Biff is a jerk.

In November 13, 1955, Biff would transport her in his car to Las Vegas, Nevada, so she could play the slot machines, and she would insult him while he was driving.

On March 27, 1958, Biff lost all his money betting on horse racing causing his grandmother Gertrude Tannen to scold Biff.[3][4]

Gertude died some time before 1985.[5]

Hell Valley Timeline[]

In November 12, 1955, in an alternate timeline, Biff received a sports almanac detailing fifty years of sports statistics from his older self who came from the year 2015. Since he was only seventeen, he couldn't legally bet, so he gave money to his grandmother to bet on the Chicago Bears. She didn't bet on the Bears, and lost, making Biff twenty dollars poorer. Biff told her to make another bet, on the Washington Redskins. However, she only gave Biff back his twenty dollars, and kept the rest for himself. When Gertrude claimed Biff was as greedy as his father, Biff stated that he learned that from her.

Biff later was approached by a shady man named Uncle Lou, who saw Biff using the almanac to tell his grandmother which teams to pick. He killed Gertrude, and put her in the back of his car to bury her. He planned to steal the almanac, kill Biff, and bury him next to her. However, when he went to hit Biff with a tire iron, Biff caught it and killed him instead. Biff justified the murder in his mind based on the fact that Lou had killed his grandmother. He buried Lou, and took all of the money that was in his briefcase. With the money, he covered up the murder of Gertrude by paying to have a death certificate forged that stated she died of natural causes.

Later at school, Lorraine Baines offered her condolences for the loss of his grandmother, and Biff tried to proposition her, before clumsily trying to apologize for his actions at the Enchantment Under the Sea dance.

Biff then tried to use the death of his grandmother as an excuse to Principal Stanford S. Strickland for his repeated absences. When Strickland told him he would be repeating his senior year for the third time, Biff tried to bribe him with some of Lou's money. Strickland then expelled him from school, and Biff stated that he intended to drop out.

Behind the scenes[]

  • Gertrude Tannen was never shown on-screen, but her voice was provided by Thomas F. Wilson — notably where she is yelling at her grandson Biff (also played by Wilson).
  • Tom Wilson stated in an interview that the incessant nagging from Biff's grandmother may be the primary reason Biff grew up to be so mean. She could be heard yelling at Biff the night of the Enchantment Under the Sea dance.