When the two fought in Tokyo three years ago, Harrington trailed after the first round, but frustrated Ferreira with her neat footwork and technical boxing to ultimately win on points and claim the gold.
This time around, the Irishwoman controlled the bout and prevented Ferreira from turning the fight into a slugfest as she ducked and weaved while landing some crunching blows of her own.
"It just feels fantastic to get that fight out of the way, because Bea is a fantastic opponent and since Tokyo she's gone on to do great things in the professional ranks," Harrington said.
"I felt like I was the underdog in there today and I knew she had a point to prove."
Ferreira, who will not fight in amateur competitions after the Olympics, said she did not have any regrets after ending with bronze, adding: "We plan one thing and God does the other.
"I wanted to be in another final. But I managed to complete a bit of the mission. I wanted to have another medal. Half of the mission was a success."
Harrington will take on China's Yang Wenlu in the final, who beat Wu Shih Yi of Taiwan.
Asian Games champion Yang put on a masterful display at the North Paris Arena to completely dismantle her opponent and score a unanimous win.
Yang's compatriot Wu Yu, the Asian Games and world champion, also won in the flyweight division, dispatching Thailand's Chuthamat Raksat with ease.
Defending welterweight champion Busenaz Surmeneli of Turkey lost to Thailand's Janjaem Suwannapheng, who will next face Algerian Imane Khelif - one of two boxers caught up in a row over their eligibility at the Paris Olympics.
Earlier on Saturday, Philippines' Carlo Paalam, a silver medallist in Tokyo three years ago, was eliminated from the featherweight category by Australia's Charlie Senior after a split-decision win.
"This feels amazing. It’s a dream come true. I’m just grateful I could do it in front of all my fans and family who were here to support me," Senior said after assuring a medal for Australia.
Uzbek duo Abdumalik Khalokov (featherweight) and Asadkhuja Muydinkhujaev (welterweight) clinched 5-0 wins in their respective quarter-finals to progress to the last four and add two medals to the country's tally.
"It is also my dream to be an Olympic champion. My parents are praying for me to be an Olympic champion. And I will be one," world champion Muydinkhujaev said.