Authorities responded to a home in the 14000 block of Mulholland Drive in Los Angeles at 8:16 p.m. Monday. Armstrong was pronounced dead at the scene. He was 47.
According to the L.A. County Coroner's Office, Armstrong was found hanging in his bedroom. There was no suicide note.
An autopsy is scheduled for Wednesday.
Taylor Armstrong had filed for divorce a month earlier, citing irreconcilable differences and seeking legal and primary physical custody of their daughter, Kennedy.
A spokesperson for Taylor Armstrong said the reality TV star is "devasted by the tragic events that have unfolded."
"She requests privacy at this time so that she may comfort her young daughter. Her thoughts and prayers are also with Russell's 11- and 13-year-old sons," said spokeswoman Jane Owen in a statement.
Russell Armstrong was an investment banker and founder of Crescent Financial Partners.