Theresa Magdalena Margarita Ann Russo (née Larkin) is the mother of Alex, Justin, and Max Russo. She runs the Waverly Sub Station with her husband, Jerry Russo. As a mortal, she possesses no powers, but encourages her children's discovery of things such as school and their Latino heritage (Alex and her brothers are half Mexican from Theresa's side of the family). She does not like magic, and she can not stand when she finds "magic running amuck in the house."
Theresa Russo is a typical mother. She's fussy, caring, and can be pretty embarrassing. Theresa lives in Waverly Place in Manhattan with her husband, Jerry Russo, and their three children: Justin, Alex, and Max. Unlike her children, she is a mortal. She dislikes magic probably because she was once possessed by a Wizard's love spell for twelve years.
- She was wildly popular in high school, which she mentions several times. Though she skips over the fact that she was the first girl admitted into a formally all boy high school.
- She absolutely hates magic and can't handle a wizard class without getting annoyed. However in "Max's Secret Girlfriend" episode, she was screaming "I'm a wizard freak!"
- She thinks that because she's not a wizard she can't get in trouble for wizard laws.
- In all the Main Characters she is the lowest in appearance in all episodes unlike Alex because Alex appeared in all episodes.
- She is revealed that she want the Sub Station to be destroyed permanently as seen in the episode Wizards Unleashed
- She doesn't understand what magic is used for because in the episode Night at the Lazerama Alex said that on the way home (from the lazerama) she learned a spell that could turn a person into a pair of socks (Argyle, bobby, tube knee high into socks turn this guy/girl) she says "Max only wears the same pair of socks anyway, so he could just wear Conscience" (portrayed by Moises Aries)
- She is portrayed by Maria Canals Barrera.
- She's only taught a brief wizard lesson until the kids start fighting and she yells, "Alright, I quit. Justin, it's on you!!!"
- She is said to be a fast swimmer in Wizards on Deck with Hannah Montana, always winning first place, mostly because she was afraid of swimming and couldn't wait to get out of the water.
- She is one month younger than Jerry Russo.
- She doesn't like when her children use magic around the house.
- She wanted to have quinceañera when she was Alex's age, but her family couldn't afford to give her a party, so Theresa didn't get to have a quinceañera.
- She thinks she is very young for her age.
- She also can never forget about the "black hole in the sub station" incident
- She was once possessed by Giselle when Giselle kidnapped Theresa and pulled her protoplasm out and turned herself into a demon and possessed Theresa's body for revenge.
- She is the one Alex usually comes to when she has a problem that is non-magical.