Teresa is the oldest of the Brisby children and the most mature. She was voiced by Shannen Doherty as a 12 year old and Jamie Cronin as a 16 year old.

Secret of NIMHEdit

Teresa is first seen in the Brisby house where she, Cynthia and Martin are home alone until Auntie Shrew arrives asking for Mrs. Brisby. Teresa tells the Shrew that their mother is not home but the shrew insists on waiting for Brisby's return. Teresa tells Auntie Shrew about Timmy's condition as Martin claims he is not scared of anything. Auntie Shrew tells Martin to "hush up" but Martin snaps back, provoking an argument. As this happens, Teresa tries to stop Martin by whispering his name in desperation to no avail. After Martin calls the Shrew a loudmouth, she decides to leave but falls down the stairs. Making the children laugh, including Teresa who is trying not to laugh. At that moment, their mother returns and is warned of Moving Day by Auntie Shrew. When Mrs. Brisby scolds her children by saying "Well children, now you've done it.", Teresa tells her it was Martin and smiles. As their mother gives Timmy his medicine, the children carefully and quietly watch as their mother tells them the cause of Timothy's illness: Pneumonia. Teresa is in several scenes after this, one in particular involves Jeremy the Crow suspended by his own string and 'interrogated' by the children. She is seen in the scene where the house sinks in the mud, calling to her mother for help. When Cynthia falls into the mud, Teresa pulls her out with her foot. She is last seen with her whole family at the end of the movie.

Secret of NIMH 2: Timmy to The RescueEdit

Teresa, along with her siblings, appear in the sequel for a short time in the scene before Timmy leaves for Thorn Valley. But, playing a smaller role than Martin and Timmy, she only appears briefly.