Kimberley RMCP were called to a home Friday in Marysville, a suburb of Kimberley.
Officers found the body of a man inside, and determined that his death appeared suspicious. Officers secured the scene and called in the Southeast District Major Crime Unit to gather evidence.
Police announced the victim's girlfriend had been arrested on Saturday night.
Cpl. Chris Newel said she is being held in custody pending a court appearance.
"The investigation is still in the early stages and police have not confirmed the cause of death," Newel said in a written statement.
"Police would like to assure the public this is not a random act."
Marysville is five kilometres south of Kimberley, and roughly 25 kilometres northwest of Cranbrook.