Harris was last seen leaving for work but she never showed up.
Harris' family says she has a restraining order against her estranged husband, Curtis. They say he was recently released from prison after spending two months behind bars for allegedly kidnapping her and threatening to kill her.
Upland police say Monica Harris might have been taken against her will in her own car, a dark blue 2001 Ford Expedition.
If you have any information about where Monica Harris may be, you're asked to call the Upland Police Dept at (909) 946-7624.