New evidence emerged on the incident that saw the 27-year-old arrested and banned for two games by the NFL earlier in the year, as Rice was shown to have punched his wife Janay Palmer in the lift of an Atlantic City hotel.
The club cut ties with Rice and the NFL decided suspend him indefinitely following the emergence of the video.
Harbaugh told reporters: "We had a chance after seeing video to meet and came to decision to release Ray. It's something we saw for first time today it changed things."
When asked why the Ravens hadn't seen the video until Monday, Harbaugh added: "I have no answer for that."
Rice had been with the Ravens for six years as the club selected him in the second round of the 2008 Draft.