She works as a maid for Maris and Niles Crane. Marta was born in Guatemala, and fluently speaks Spanish and German. She learned German when she worked for a German family 'who showed up in Guatemala after the war'. As Maris remains offscreen, her words are often conveyed by Marta. She becomes Marta the Mole for Niles when he is kicked out the house. One Halloween, Niles mentions that she is severely arachnophobic.
- In the first season, it is said she was seventy-eight years old. This puts her birth date at around 1915 or 1916, making her almost ninety at her last appearance.